Area 51 Cheats
Gray Alien in multi-player mode
Finish campaign mode under the hard difficulty setting. You can also finish the game under the easy difficulty setting. Then, go to the last level and complete it under the medium difficulty setting. You will then have the choice to play under the hard difficulty setting. Choose to play the last level under the hard difficulty setting and...
Find and scan all five databank items in a level to unlock the secret for that level. The final secret of the game is unlocked when all prior secrets have been found.
Complete campaign mode under the medium difficulty setting.
Masons and the Illuminati
Shortly after meeting Dr. Cray, you will reach an infirmary where you will find clones of Mr. White walking around, mumbling, and rambling on. On the back of their lab coats you will find a Masonic lodge (a symbol of the Free Masons) suggesting a connection between the Masons and Illuminati.
To defeat Grays that use shields, mutate and fire parasites at them. It will bring down the shields faster than any other weapon in the game.
In the moon landing room, after you activate the crane, shoot the earth, go on top of the catwalk.Â Make your way to the earth and drop down for extra ammo, etc.
How to beat the Theta
The best way to defeat a Theta is to first mutate. Next, fire parasites; or if you want to take a chance, fire contagion to lay some heavy damage on him. REMEMBER: Use contagion for heavy damage, but parasites also work well, especially because they heal you. When your mutagen runs low, run up and melee him and/or the enemies he releases on you...
During the training levels, scan everyone that you can. You will find some interesting equipment of the MPs, including adult diapers and condoms. Hold Right Analog-stick Down (with the default controller configuration, or in the opposite direction in the inverted configuration) until your scanner stops moving and you appear to be looking at your...
How to beat the Super Beast
When fighting the Super Beast, rather than running straight at him, run around in a circle. When he gets near an explosive barrel, shoot it. It does more damage then the BBG. Watch out for his plasma shooting arm as well. When you finish, Edgar will talk to you, and you get to see him.
Life Or Death Alien grenade upgrade
Search the dead soldier in one of the elevators where Cole starts the level to find a small key. Use it to open the small lockers in the first power conduit pit to find a databank item. It will upgrade the alien grenade so that it will track targets.
In the earlier stages of the game, there are a few cabinets of the original Area 51 arcade game, complete with red and blue light-guns. REMEMBER: Melee attack the arcade machines and you will usually get a life syringe.