All Working Area 51 Cheats - Xbox

Secret tapes
Scanning all five databank items in each stage yields one secret. Completing the game yields one secret.

Secret Rooms
Level 2: Shoot all the highest windows in the far wall in the hangar. When you are in the truck, shoot all yellow barrels, and you will discover another secret room.
Level 4: When you are driving on the STAAR jeep, shoot every yellow box.
Level 5: Shoot the sign which shows the words General Weatherby on the second door right away when this door opens.
Level 7: Shoot all yellow barrels in the first area where the four purple zombies are throwing barrels.

Infrared
If you start the game, only shoot the first three STAAR team members. If you do this right, you will have an infrared sight.

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.

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.

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.

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.