Well, I just use them in either edits or DMs/TDMs/Zombie fights. I know, you people have different opinions about add-ons and whether to get all of them, or just the good ones (I'm not asking you, just so you know), but I like some variety in the fights. Some people like to sniper, while others go for close combat. Some people like to be trigger happy with the P90, while others like short-but-powerful shots with a pistol.