Kill 5 enemies in a row using 5 different weapons or attachments in Single Player or Special Ops.

You can get this on any campaign or Special Ops mission.

* The best places to get it are missions where you start off with a weapon that has either a grenade launcher or shotgun attachment.

First, simply kill an enemy with your primary weapon. Then kill an enemy with your grenade launcher or shotgun attachment (provided that you have one). Then switch to your secondary weapon and kill another enemy (This is 3 kills so far in most cases). Then pick up another weapon off the ground (maybe off one of the enemies you just killed) and kill another enemy and then do the same thing with another gun you picked up off the ground you will get the achievement.

Note: You can try using your knife as one of the weapons, but I'm not sure if it works or not. Just try using the original tutorial above to get it the first time.