Revolver is an obtainable item from the Better Dungeons mod. The Revolver so far seems to be only obtainable in the dungeons, no crafting recipe to be found. It is seen used by the Pirates, and can rarely be found in chests in dungeons. It uses bullets and has no cooldown.
The gun does 7-8 base damage. Its accuracy at longer range is unimpressive, so it is advised to keep it as a short range weapon.