The sub machine gun ( or SMG) is a small machine gun that doesn't hold much ammo and doesn't do much damage but you move lighter. Most of The Armored Werewolf's loadouts on BO2 have SMGs. And the Sniper from TF2 has an SMG for a secondary weapon. These weapons can be useful if you are in a rush to kill your enemy, but it doesn't go very well when it comes to a swarm of enemies. Most COD games have SMGs.