A modified .223 rifle that was cut down to a pistol. It has two triggers, two red LEDs, ejection port, a bolt handle and an ammunition capacity of 5x .223 - giving it excellent firepower. A very rare weapon in the Core Region during 2161, becoming more popular amongst the gangs in and around New Reno in 2241.
A modified .223 pistol with only one trigger, two red LEDs on the side, a large yellow LED on the back, an ammunition capacity of 5x .223 or 5.56mm round, a motorized cylinder and crane - for quicker shooting and reloading than a typical revolver.
According to Joshua Sawyer, the name "That Gun" is derived from the fact that players would refer to the .223 pistol from Fallout and Fallout 2 as "That Gun".
The .223 pistol was planned to be included in S.T.A.L.K.E.R.: Clear Sky as an easter egg, along with the Bozar and generic .223 ammunition, but only remains partially implemented in the game's resources.