The Pup is a single-shot, break-action grenade launching pistol. It is manufactured by the Helghast, and used by Helghast officers rarely in certain missions later in the game. it is found extensively in multiplayer maps.
The Pup fires grenades in the same manner as the Grenade Launcher, but does not reduce movement speed. It should be used while in cover, as you will need the time to reload. Do not rush into a room full of enemies with it equipped, as you will most likely fire one shot and just die. Instead, stay by the door and fire individual shots into groups of enemies to save ammunition. It is also very effective when firing over cover, as its large gravity drag means that a well placed 45°shot will kill any enemy on the other side of cover.
Try not to prioritise the Pup as your main weapon, and instead treat it as a sidearm in difficult situations. When available, drop it for the larger Grenade Launcher due to its larger ammo reserve and rate of fire.