There is no greater tool at the disposal of players in Call of Duty Zombies than the Pack-a-Punch machine. Debuting back in Der Reise in Call of Duty: World at War, Pack-a-Punching a weapon will not only double damage and magazine capacity (and in some cases add epic side effects like making pistols fire explosive rounds) but will also give a player's weapon a cool futuristic camo and a laser-like pew-pew effect to the sound of the gun firing.