Doom 3

After you have found the lost scientist and are returning to the main building, find your way back to the bathrooms. Stand in front of the mirror with your pistol then cycle through until your shotgun then get very close.

Cabinet 001: 396
Cabinet 003: 483
Cabinet 009: 752
Cabinet 013: 586
Cabinet 017: 347
Cabinet 023: 531
Cabinet 038: 409
Cabinet 039: 102
Cabinet 047: 123
Cabinet 048: 123
Cabinet 049: 123
Cabinet 054: 246
Cabinet 054 (second): 142
Cabinet 063: 972
Cabinet 064: 651
Cabinet 078: 364
Cabinet 079: 364
Cabinet 103: 259
Cabinet 104: 579
Cabinet 112: 538
Cabinet 114: 715
Cabinet 116: 972
Cabinet 116 (second): 624
Cabinet 117: 624
Cabinet 213: 371
Cabinet 215: 298
Cabinet 216: 624
Cabinet 217: 624
Cabinet 317: 841
Cabinet 386: 836
Cabinet 387: 836
Cabinet 452: 571
Cabinet 666: 372
Cabinet 669: 468
Martian Buddies 1 and 2: 0508
Monorail Override Junction 5: 826
Monorail Override Junction 5 Junction 7: 953
Weapons Storage 1 and 2: 584

When you get to Mars City, go to the kitchen. Look closely at the video game in the back to see a classic Doom screen while you punch the turkey.

Hold the left trigger and press: X, Y, B, A a sound of a demon will confirm the cheat.

Be prepared to die a few times. Beware of the edge of the room, as you can fall off. Also, do not hide behind the pillars for too long. They will open up and arc electricity periodically. When you walk into the room, a giant bay door at the
opposite end of the room will open, revealing the "new and improved" Sarge. As soon as that door opens a crack, start lobbing rockets in there. After you score about six good hits without being splattered by his BFG, break out the Soul Cube (that you should have charged before entering the room) and let him have it. It should kill him and heal you. Pick up the armor and ammunition around the room before continuing.

When you each the end Boss, do not bother wasting your ammunition on him. Just stay away from him. Kill the Imps and other demons and use the Soul Cube on him. If you are play in co-op mode, shoot him. Use the Soul Cube on him about
five or six times. On the last time you will see an intermission sequence of him dying.

When fighting the Guardian Of The Soul Cube in hell, do not bother shooting his body. This is a waste of precious ammunition. Instead, blast his "searchers" with something with good coverage like the chaingun, and he will have to spawn more. When he does, a blue light will appear over his body. Shoot it with the rocket launcher. Do this a few times and he will die easily. Also, look in the room around the columns for ammunition, health, etc.

On the last level before you go through the portal to fight the boss. Their is a stone tablet somewhere in the last room. If you look at it you can see the picture of the original Doom cover.

Enter one of the following codes during game play. A sound will confirm correct code entry. Repeat the code to disable its effect.

Doom Ultimate And Doom 2: Toggle God And Degreelessness Mode
Hold L and press A(4).

Doom Ultimate And Doom 2: All Weapons, Health, Keys, And Armor
Hold L and press B(4).

Doom Ultimate And Doom 2: Temporary Invincibility
Hold L and press X(4).

Doom Ultimate And Doom 2: Full Map
Hold L and press Y(4).

Doom Ultimate And Doom 2: Berserk Mode
Hold L and press X(3), Y.

Doom Ultimate And Doom 2: End Level
Hold L and press A(2), B(2).

Doom Ultimate And Doom 2: Chainsaw
Hold L and press B(2), A(2).

Doom Ultimate And Doom 2: Invisibility
Hold L and press X(2), Y(2)

Doom Ultimate And Doom 2: Light Amplification Goggles
Hold L and press Y(3), X.

Doom Ultimate And Doom 2: Radiation Suit
Hold L and press X, Y(3).

The projectiles thrown by the imp and hellknight can be ducked if you time it correctly (it will do no damage). Naturally, you want to do this against enemies on the same height as you, not on shots coming at diagonals.