BFG (M249 SAW) in City Streets level:
Enter 5SQQ-5THA-ZFFV-7XEV as your profile name. Make sure you include the "-" symbol when entering the code (located next to the "!" symbol). After selecting "Done", you will be able to re-enter an actual profile name. This is how you know the code was accepted. When you begin the first level, you will have the BFG weapon.
Alternately, enter one of the following profile names:
Successfully complete the game under the normal or hard difficulty settings. All guns will now be silver and have unlimited ammunition. Note: The silver weapons will only be available for the difficulty setting you have completed and any lower difficulty settings. This does not include the Black Ops difficulty setting. You will always have silver weapons on that setting.
Black Ops difficulty setting:
Successfully complete the game on the hard difficulty setting.
Successfully complete the game under the Black Ops difficulty setting to unlock the M16A2 (M16 with grenade launcher) for use on any difficulty setting.
Faster M16A2 reload:
With the M16A2 in Black Ops mode. the lag-time on the reload for the grenade launcher is long. Immediately after you shoot a round, switch weapons then switch back quickly and it will be reloaded for you.
Quick suppresser set:
When you are in the middle of putting a suppresser on your weapon and enemies appear, fire and the suppresser with be on with your weapon going instantly into firing position.
Use destructive objects to your advantage to shock, hurt or even kill your enemies.
Defeating enemies with shields and body armor:
There is no real secret to use with enemies with full body armor. Head shots will not work; just shoot. For enemies with shields, use grenades or RPGs. Or, get behind them and kill them by shooting them in the back.
Aurora stealth plane reference:
In the first mission, under any difficulty level other than easy, you can destroy Intel as a secondary objective. One of those Intel-containing laptops once destroyed holds information on an "Experimenting aircraft code named 'Aurora'." The "Aurora" is supposedly a real, yet secret, aircraft. Most of the Intel is real or based on real world information.
Defeating RPG troopers:
Whenever you encounter an RPG trooper, the easiest way to take them out to is to wait until they fire a round (pop out then hides behind something). While they are reloading, shoot at his midsection. If successful, you will shoot and detonate the RPG he is trying to reload, blowing him up.