Demoman's loosecannon but the fuse is reversed.
The timed fuse starts from 0 second, but it charges up to delay the detonation.
It's said for everything but, add minor negative stats to balance out the overall performance. The negative effect should be something to reinforce the intended playstyle. In this case, damage penalty for not charging up. Charging the weapon to the maximum range retains the original damage. It might be too spammy DPS-wise. It can be low explosion radius instead, to make him struggle more at close-range like any other pipe launcher.
For it being more unique, I'd have no double-donk functionality. Directly hitting the opponent must cause the explosion instantly, regardless of the fuse.
For the soldier's rocket launcher concept above. I recommend something like, -25% projectile speed. It allows players to have more precise controllability for the gimmick, yet itself being a penalty for the overall performance.

Soldier's rockerlauncher - Delightning
The rocket goes straight until a certain point, then the rocket goes downward.
The possible trigger, timed fuse, m2, or even m1 (fires next rocket in that case,)
The point is to use it like a detonator. The explosion happens at the foot of the opponent.
You can also attack someone under the cliff, or behind the wall. As long as there is a place for the rocket to fly above the target. M2(alt-fire) would be the best trigger mechanism.
The name spelling De light"n"ing is intentional, as it's a pun for saying the lightning(thunderbolt).

Sniper Rifle that keeps charging without scoping but takes twice as long to fill the meter.

Throwable scout pistol concept
Instead of reloading he throws his empty(or not) pistol. The game shows how many times you can re-equip the gun, instead of the whole rounds. The thrown pistol deals exceptional damage to the opponent, he can reload 2 times. 12 rounds in the clip + 24 rounds (2 extra pistols) reserve. Compared to the stock 36 reserve ammo it's less. He gets another gun out of his pocket, if you reload at 7 rounds remaining the trashed ammo goes nowhere.

Second idea : All of it above plus damage ramp up per successful hit. The thrown pistol's damage is added 5 for each shot landed on the same opponent without reloading. Instead the thrown pistol's base damage is set to 0, with the maximum damage of 60. Small ammo box restores 1 reserve pistol. Damage ignores range.

Headshot bat - melee with headshot registration, slows enemy in the head. No damage gained. Slows wearer regardless of the presence of enemy, -20% slower movement speed for equipping this weapon. Works like Natasha, the effect stacks up.

Enigma decoder - WW2 air raid siren banner for soldier secondary, reveals enemy HP on use. Nearby teammates gain the ability to see the remaining health of the enemy. To see enemy HP you don't have to be exact about the crosshair but there is a threshold for showing the HP or not. This item explodes on death, to protect the important secret of this tool. The delay is 0.3 seconds and deals no damage, purely cosmetic.

Deadline knot - syringe gun - hitting the syringe for the first time marks the enemy for 5 seconds. As the tag is removed, 10 damage is dealt for the time you hit the enemy with the weapon. The flying syringe deals up to 5 damage, the delayed effect does twice the damage. Healing yourself with medkit or medigun removes the effect without triggering the effect. Stock syringe gun at close range deals 12 per shot, and the falloff is kinda off. Stock syringe gun is actually good at long range burst damage, this is not much of an upgrade. syringe gun has an attack interval of around 0.1s, 10 syringes are fired in an 1 second burst. Normal syringe gun deals 120 - 90 damage from directly hitting the enemy, this gun deals 150 - 140 damage (50 damage + delayed 100 damage). Medic having this weapon drops a small medkit upon death.

- Emitter medigun - Something something laser pun, pain eraser. laser type medigun that requires consistent accuracy and constant guidance. Very competent medigun with triple the range. It penetrates teammates up to 3, heal rate ramp up mechanism is removed. But healing the same target for longer period of time accelerates the healing rate.

- Blood bond - Medic melee - Swinging it without hitting anyone deals self-damage, it charges its own meter from doing it. Attacking teammate with this weapon overheals the target for the amount of the charge. When you are safe, you use this weapon in moderate fashion. Then use it to your teammate when you need it. The max charge heals teammate 150 HP, this weapon adds to the overheal but doesn't exceed the scripted limit. It takes 5 swings to fill the weapon. Each swing deals 30 damage to the medic himself. Attacking enemy with this weapon doesn't charge the weapon. Can be used without charging to max.

-Lunar hope- Medic's medigun - If the Ubercharge is at full, upon death the one you kept healing gets 6 seconds of kritz and invincible. The medigun requires medic's death to activate the uber. Pressing m2 at 100% kills the medic, killbind works too. Beside that the performance is the same with the stock. Just more dramatic. The Uber duration is slightly shorter 75% compared to the stock 8 seconds. After death the spectator camera is automatically set to the one that got the uber.
Names I think are good, Warning gibbous, Fullmoon hope, Eclipse brights.

-Tiarra- Medic's medigun. Press m2 to toggle uber, can be used without charging it to 100%. The uber is replaced with the MVM shield. 4 seconds duration at maximum. The idea is to deploy it almost like an airblast. To counter projectiles, even good for a sniper rifle. A medic having this medigun is no longer counted for capping the point. The shield itself doesn't deal damage in contact.

- Lurking licker - Candy bag, a melee for medic. When the medic dies, he spreads small candies for the area. If players are hit with the candy, the players are healed for the amount of Ubercharge you had at the time. The amount of heal is % equivalent of the lacking HP, maximum health - current health = lacking Health points. If you are 150HP class with only 50 HP remaining, your lacking HP is 100. If you are healed from the candy medic dropped when he was at 80% UberCharge, you get healed for 80 HP.

- Precast spills - Medic primary item - Portable ice cream machine. 4 selections of chems you can deploy, the item you selected is dispensed like a sandvich. Reload key to cycle the types. The types varies 1,healing (with the effect of a medium kit) 2,bullet proof 3,explosive proof 4,fire proof. 3 chems can be placed at the same time, it takes 30 seconds to be able to place the chem again. These 3 resistance buff items are corresponding to the specific damage type, like Vaccinator. And it gives 35% damage reduction for 1 minute, fireproof kit keeps a player safe from afterburn by reducing the damage to 1. Medic can take it himself too. The kit is team colored and only the medic's teammates can be affected. These are ice cream with the Vacc's icons indicating their resistance types. Sure medium medkit is easier to read the logo, but they are to large to call them "portable" lore wise. The machine shows a 3 test tubes connected at the neck containing RYB colored liquid. The item disappears after 20 seconds after deployment. If enemy players take the item, it always heals them instead of giving them the resistance, and it heals fixed 15hp.

Mistic realm - Medigun. Standing still generates a healing field. Basically an automatic amputator taunt, still maintaining your ability to use the medigun. -30% movement speed while using the medigun. Uber generates a healing field with much bigger radius for 7 seconds and moving yourself doesn't matter. The healing field from the uber ignores walls, a normal healing field doesn't. For some reasons, it takes 0.3 seconds to form the field. If strafe-walking produced the visual appearance of the field, it would suck hard. Heal rate is 5 hp per 0.5 seconds, Uber boosted healing is 15 hp per 0.5 seconds. This Also heals the medic himself.

Pandora - A rocket launcher. Attacking enemy with this weapon reveals the enemy HP for 0.5 seconds. Only visible to the soldier. -25% clip size.

Raider - Flare gun. Crits against non-burning enemy. Sets enemy on fire. Base damage of 24. -20% damage. -66% afterburn damage.

Compensator - Scout primary with a huge compensator. Firing the gun pushes you forward. 8 self-damage per shot. The vector is limited to horizontally coordinated way, firing upward or downward vertically cancel the momentum and the scout doesn't get any benefits out of it. If you fire at 45 degree angle, the force is halved.

Horrow descender - Scout pistol - You gain 3 extra jumps but each jump height is halved as you jump more, fall-damage is 4 times stronger. Your second jump is halved, 3rd jump is 25% jump height of the first jump. Soda popper is affacted.

Air strafe - A rocket launcher that only allows you to fire at a maximum incidence of 15 degree from downward. After 2m from launch, the projectile stops propelling itself(visually) and start the "free fall" sequence. 50% more clip size meaning 6 rounds max. The rocket is bomb shaped. Rocket jump is completely normal because you'll get the same ballistic until it stops going straight.

Chain reactor - Hitting old stickies with new one causes it to explode, the explosion detonates other stickies if they are in the range, and the sticky detonated by other stickies produce much bigger explosion. It stacks 8 times maximum hence the limitation. Each time buff the damage 1.3 times.

Tracing runner - Scout's secondary. It's always active as long as you have the item in the loadout. Scout has a tape and it flutters behind him, blocking other players to path around it. The idea is to run circle around enemies, like a sonic in the new frontier game. The scout can't do much to disable enemies' ability to play the objective, simply because the scout's health is so low. If the scout is ignited, the tape turns into a crisp.

The doctrine conductor - Spy's revolver. If there is no enemy beside the target, the revolver always deals 300% more damage (not crits). 50% Chance of firing the bullet, half the time spy loads a blank instead. Taunt is a Russian roulette. The game checks if there is any sort of sight inline, assuming that you are fighting an isolated enemy.

The pop downer - Sticky's damage increases as you keep it on the ground. The sticky starts emitting crits aura even tho they aren't crits. Maximum ramp up of 30% damage increase, it takes 30 seconds to reach the max damage. The downside is slow fire rate of only 70%. The stat is -30% rate of fire.

Also the before mentioned Bullwork resembles an anchor. And a soldier swings it like a normal pickaxe. It's a namesake of bulwark.

These 3 concepts were what I wanted for new different weapons, but it just sounded like a way I want normal sniper rifles to be. So I name it
"Steady Steady" - range of only 7m, charging it extend the range exponentially to the point of near infinite(never happening). Non-scoped shot deals 90 damage instead. Scoped HUD shows the range with "sentry range indicator" you see when you are building one. But the problem is, it's not spherical. The point non-scope bullet stops registering is highlighted with a bright light (blue). As if the bullet is hitting an invisible wall at the set distance.
"Aimwell" This particular sniper rifle's bullet has a massive damage falloff. Charging it regain the original damage up to 80%. Always 60% faster reload.
"Wattsup" Laser rifle, firing the weapon fills the overheat meter. The meter increases the charge rate. The "heat" meter is reduced over time and how much you charge the gun is not affected for how much heat is experienced per shot. When the meter reaches maximum, it automatically goes cooling mode. The cooling mode rapidly decreases the meter, the gun starts firing low-damage shotgun instead. The point is to keep it hot while not exceeding the limit. If you are playing this way, you can switch to shotgun mode conveniently at will.
About the "Gazeback" I presented above, I explained a little less. It partially replaces the charge up meter with differently colored bars, and the bars are chosen almost randomly. But it has some rules, very first seconds are prevented from becoming the red area. Also the very last is separated from the potential red area. If you press R at the moment your charge is at the red bars, you don't have to unscope until the next reload. You can keep cycling this action.

About Nectar, or a different weapon candidate. Self-knockback even when you are grounded.
Reactor shield further explanation ; The 100 damage cap is an explosion-only effect, it doesn't block the damage for the damaged demoman himself.
Hothr has long range, it fires liquid form piss at very high velocity. The base framework is flamethrower.
A player can pickup thrown Landsman. Landsman travel through air spinning. The projectile absorbing mechanism can be reworked, it might be better being "blasted to random directions".

Sniper rifle rebalance ideas, 3 different methods.
Sniper rifle now has a limited range, but charging the rifle increases the range ( long enough to snipe across the map)
Sniper rifle now has damage fall off, but charging the rifle retain the maximum damage up to 100%.
Sniper rifle now overheats if you keep shooting the rifle, the accuracy decreases. It takes some time to cool down your rifle, recommend charging your shots.

New wet functionality for Pyro's green gas. If a player with "wet" effect is ignited, the effect is now overwritten with a "fire-lock" state. What fire-lock does, is that it requires additional effort to put the fire out. The first medkit you take remove the effect but keeps you on fire for once. So you have to take 2 medkits to save yourself from the afterburn. Dispenser or medic's medigun remove the effect but they also take the extra effort to extinguish you.

Clare - Pyro's secondary
Bleeds enemy on hit for 4 seconds, base damage is 50 instead of 30. Always crits on a bleeding target. Deals mini-crits damage on a burning target. If the target is meeting the 2 conditions, it always crits instead of dealing mini-crits damage. bleeding state deals 4 damage per 0.5 seconds, 4 seconds of bleeding results in 32 damage at maximum.

One Mann armory - Soldier's secondary
Apply "death marks" on nearby enemies, the damage required for the banner is 500 instead of 600. Players marked for death takes mini-crits damage. It's helpful if your teammates deny to rush in.

Landman - Scout's melee
Alt throws his bat, direct hit on the head stuns enemy completely. Absorbs projectiles on the path. If they are explosive, the bat explodes on contact with solid objects. Name might be Landsman but ok.

Duka cola - Scout's secondary
Adds "self-knockback" to all his primary after consumption.

Nectar - Scout's primary
Alt fires both rounds at the same time. Force-a-nature without the knockback only for enemies, scout still gets propelled.

Bullwork - Soldier's melee
Deactivate fall damage while active. -20% swing speed.

Yuri - Heavy's primary
Can shoot the gun without completely spinning it. Requires firing to rev up. Fire rate ramp up over time as you've had it spun up. No alt-fire functionality. Instantaneous firing from 0 spin. (Easier to imagine as a revolver cannon, it explains better than me.)

Concussion - Spy's disguise kit
Replace the position with the target enemy and disguise yourself at the same time. Oh no it's not balanced. Then. Disguise yourself as the target enemy(on your crosshair) instantly, without smokes and noises.

Reactor shield - Demo's secondary
If demo wears this, every damage dealt to demo creates an explosion of the equivalent damage. The radius varies with damage dealt. Never recharge his "charge" meter, only way is to take the resupply shelf in the spawn room. If the damage is over 100, fix the damage at 100 and never register the rest. No resistance gained from this shield.

Artisan - Demoman's primary
Doesn't travel much horizontally. The projectile gets extra velocity when the shooter is facing upward, the extra velocity can be used to land the pipe far away from you. A classic mortar. The projectile deals more damage if the pill is existing longer in the air. Explodes on impact, works on any surfaces. Stores up to 6 rounds on a clip. 30% explosion radius minimum, 130% explosion radius maximum. 60% damage minimum. 100% damage maximum.

Spirit sword - Demoman's melee
The range is greatly enhanced, it visibly shoots the trails of the sword. 10% weaker base damage, the ranged damage has falloff. Can't crits or mini-crits no matter what, even with banners, kritz uber, nothing works with it. Classic "Oh, it's cutting through the air" troops.

Hothr - Sniper's primary
Water gun filled with piss, basically a piss thrower. It shares the meter with Jarate, meaning you can't use them both at once to be efficient at making more piss. It consumes Jarate's refill meter as ammo. It is usable without Jarate in your secondary slot.

Gaze back - sniper's secondary
When you shoot your sniperrifle, creates a huge backblast behind you. The radius and damage is based on your charge, the rifle's charge. A shield type weapon, reduce 10% incoming damage from behind. As you press R at the right moment, you don't have to unscope every shot. It's like hitman's heatmaker but consistent. The moment you have to press R is notified with a special meter on your scoped HUD. As you scope, your charge meter has Red bars replacing normal orange or yellowish bars. If you press R at the moment you are charging at the red zone. Your next shot doesn't unscope.

Final frontier - Engineer's primary
Deals critical damage on a target selected by your sentry. The target under attack from your sentry is marked with a special icon only when you have this weapon. Stores only a single bullet in your clip. its entire magazine tube is removed. It somehow reuses all the animations from a stock shotgun.

Cleaner's best friend - Sniper's secondary
Water filled jar, incredibly fast refill span. Used to extinguish teammates. Wet enemies, remove "Heads" collected by the enemies.

Joint program - Engineer's wrench
Teleporters are replaced with 2-way teles that really isn't specific to being "entrance" "exit", the 3rd slot on your PDA is replaced by a second dispenser. The engi equipped with this artificial limb is damaged over time, fixed at 2hp per second. Forces the engi to be stationary near dispenser or medikit. Might be dangerous for teammates, as spies can take the tele to their spawn.

Gas lighter - Pyro's melee
While the weapon is active, the pyro's movement speed and damage is increased per burning players ignited by him.