Maybe instead of a new weapon being another gun, how about an idea for a different melee weapon. Another option for melee other than a cutlass could be throwing axes, as it can be decent for up close fights or from mid range.
Here's how it would work, you can equip 2 throwing axes in one slot for weapons, you cannot equip two sets of throwing axes (but you can equip a sword as well if your a mad man), you hold both axes in your hands, (by attacking with left click) you can chain combo hits on a enemy for 10(x1 or x2 for the amount of axes) damage per hit with a chain of 4 hits, so 80% health on a player with 2 axes for a full combo, or 40% on a player with one axe with a full combo hit.
By pressing right click you charge up a shot and throw the axe, it deals 50% of a player's health for each axe (the windup takes about 2-3 seconds and can be stopped with the press of right click before the throw) if the axe misses and lands on the ground you can pick it up, but if the axe lands in water or an enemy it cannot be picked up. The throwing axes can only be reloaded from picking up from the ground or from the weapon armory (NOT AMMO CHESTS).
Axes vs. cutlass (and other things)
Due to axes not being able to block against swings from other axes or cutlasses, while holding both axes you cannot be stunned from cutlass hits, but you can't stun cutlass/axe users either. If one axe is held you will be able to stun enemies with your swings, but you can also be stunned by cutlass/other single axe swings. The range of an axe being thrown would have to be about the size of a brigantine (before it loses momentum and lands).
