How about a radiation debuff, like slowing or health drain

+: Slowdowns and bleeds enemy for 8 seconds

–: Can be obtained only with resupply locker

Reskin: Jarate

5% slower recharge
when hitting a enemy, bleed for 10 seconds
enemys hitted, will make their screen a bit blurry
when hitting a friend, will make their melees make 5+ damage, while hitting a enemy, the enemy will bleed for 5 seconds, buff only stays for 25 seconds

snipers jarate but dousing your self has the same effect as bonk! atomic punch

The Containment Breach
+Makes a puddle on the floor lasting for 15 seconds and enemies stepping inside get a radiation debuff which is the same as bleeding but lasts for 5 seconds
-25 Second cooldown

I think this can be one of those weapons to be shared across multiple classes, like the BASE jumper. All classes that have throwables (sniper, scout and pyro) should have this weapon to use.

Level __ Radioactive Waste
+ If thrown at buildings, the building becomes stunned for 3 seconds, removing their functions, and then takes 75 damage and takes radiation damage
+ Deals radiation damage (10 damage per tick) in the area (by the way to those worrying about how to implement this, the gas can has an aoe lingering thing so Valve can work it out)
+ Affects a large area and lingers
+ Lasts 15 seconds
= Deal damage to use this weapon (500 for scout, 600 for pyro and 800 for sniper)
- You take damage in area

Crowd control and building buster in one weapon. This weapon needs careful planning to get it right unlike other throwables with more niche uses but recharging automatically. Also the stats would fit well with a molotov.

slower recharge and bleed for a few seconds in exchange for the effects of jarate

The Containment Breach
Level [REDACTED] mystery liquid
Slot: Secondary

+ Heal teammates and deals damage
+ On hit: Enemies are slowed by 35% for 8 seconds
- 60 second cooldown
- no random crits

Pros:+leaves behind a puddle of mucus (like zombie sniper abbility)
Cons:-10% slower recharge speed

Level 10 Mystery Liquid
Slot: Secondary

+Heal's Teammate's
+On Hit Enemies Lose Health
-No Random Crit's
-50 Second Cooldown

(*) Can carry up to 2 at once
(*) Enemies caught within splash radius take 20 damage up front and an additional 2 damage every 0.5s for 8 seconds. Damage-over-time stacks with itself up to 3 times. (Can self-damage, but will not apply DoT to self.)
(+) Affected enemies receive 25% less healing from all sources (does not stack).
(*) Continuous healing from Medics and Dispensers can reduce the duration by up to half. Picking up a health pack will remove the effect after reducing the healing.
(+) 25% shorter cooldown (15 seconds instead of 20.)
(-) 25% reduced splash radius
(-) Cannot extinguish fires