Have three guns
To do this trick you must have the Overkill (level 38), and the Last Stand (level 8) perks enabled. The Overkill perk should give you two primary weapons of your choice. Play a game and use this class. When you are put into Last Stand, you will get an M9. You cannot choose the pistol you want. Note: You can only use the M9 when you are in Last Stand.