BFG (M249 SAW) in City Streets level:
Enter 5SQQ-5THA-ZFFV-7XEV as a profile name. If you entered the code correctly, you will be able to re-enter an actual profile name after selecting Done. When you begin the first level, you will have the BFG weapon. Alternately, enter HQ6G-ZP3B-C5LE-WMXA or EG4P-ZGUJ-6SQJ-3X68 as a profile name. Make sure to include the – symbol when entering the code (located next to the ! symbol).
Unlock M16A2:
Complete the game on the Black Ops difficulty setting. You will now have the M16A2 (M16 with grenade launcher attachment) on all levels.
Unlock Silver weapons:
Complete the game on any difficulty setting to unlock silver weapons for that difficulty and any lower difficulty settings. This does not include the Black Ops difficulty setting. You will always have silver weapons on that difficulty setting.