Select "Unlockables" at the "Multiplayer" menu. Enter one of the following codes to unlock the corresponding weapon.

Weapon	Code
Support Kit M60 Machine Gun	try4ndrunf0rcov3r
Recon Kit QBU-88 Sniper Rifle	your3mynextt4rget
Special Ops Kit Uzi	cov3r1ngthecorn3r
Demolition Kit USAS12	aw3somef1rep0wer