Area 51 Cheats

Defeating Grays
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.

Defeating 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.

Unlock Final Secret
Grab all the other secrets to unlock the final secret.

Unlock Alien Multi-player Avatar
Beat Campaign mode on Hard difficulty setting to get alien Gray as a selectable multi-player avatar.

Upgrading The Alien Grenade
In the stage Life or Death, there is a small key on a dead soldier in one of the lifts where Cole starts the stage. Grab it to open the small lockers in the stage. One of the small lockers in the first power conduit pit has a databank item that upgrades the alien grenade.

Hard difficulty
Complete the game on normal difficulty to unlock the hard difficulty.

Moon Landing Conspiracy
When you reach "Lies of the Past: Checkpoint 4", you will ascend in an elevator. Exiting the elevator, you will see a replica of the Moon's surface, a model of the U.S. space suit, and a shuttle the United States used to reach the Moon. This is in reference to the Moon Landing Conspiracy, claiming that the U.S. never actually reached the Moon, and faked the landing to beat the Russians in the space race. The conspiracy was heavily debated, but ultimately rejected by the majority of opinions. Today, only a few people still claim the Moon landing was a hoax.

Arcade cabinet
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.

Interesting scans
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 feet. You can now scan yourself and see information about Cole.