Chaingun (Spear of Destiny)
Chaingun is played when you pick machine gun in Spear of Destiny (DOS). In Wolfenstein 3D (DOS) you also could have machine gun, but while picking you heard synthesed sound effect, not the PCM one added in Wolfenstein's prequel.
Chaingun is number 39 in the game's sound data. Its title in the VOC meta data is "GETGATLINGSND". It was named after the gun unofficially, so game's developers should be contacted for proper name.