"A damaged handgun, I wonder what it was doing down here." - inventory description
This is the second weapon you will find in the game, it is the fastest ranged weapon in the game but doesn't do as much damage as the Shotgun. It is found in the sewers, right by a human eye. It's not a reliable weapon, since it randomly jams when shot.
It appears to be modeled after the Ruger MK II pistol. This would mean it uses the 22. Long Rifle cartridge as ammunition.
This weapon's first appearance is in the nightmare section of the sewers, and it can be used to get an ending.