1st: the sword really needs a buff. It feels obsolete in the current version as of now, so a speed or hitbox buff would really help it.
2nd: the cannon doesn't really make much sense conceptually so simply changing its projectile into a slow moving rocket instead would make much more sense, then renaming it into old rocket launcher or smth, also the projectile could use a speed buff, really hard to hit bosses later on.

Weapon ideas:
Flamethrower - a bit different from all the ranged weapons. You charge up the flamethrower and depending on the charge the range and size of the stream of fire changes, does around 150 base flame damage over time. This will be the weapon that benefits on on-hit effects, so it mostly procs such items, like missile launcher and sanguine orb for example.
Sledgehammer - a slow and heavy melee weapon that knocks enemies back on hit. Can be charged for max 600 dmg, has a swing radius. Does extra 100 damage if the enemy hits a wall.
Flail - you can spin the flail around you for 100 damage per hit, charging the throw, max charge - 400 damage, the range of the throw doesn't scale from the charge.
Throwing knives - a ranged weapon that uncharged does a throw of one knife for 100 damage, you can charge them up to 5 knives to throw them in a fan formation. (most likely the attack speed is the same as handgun's)
Sickle - it's a melee weapon that doesn't have a charged attack but instead does a combo of two swings and then a spin, the two hits are 100 damage while the last deals 100 + bonus 100 bleed damage which stacks.
Shotgun - a ranged weapon that shines in close combat, shoots 5 pellets for 50 damage each, has a quite wide spread.
Chainsaw - a combo weapon that does two swings that deal 100 damage and then a boomerang throw for 200 damage.
Lunar staff - a ranged weapon with a mechanic of mana that has first 2 shots deal 200 damage, then go down to 100, mana recharges over time and has a notification when mana is back to full.