Doom (GBA)

God mode:
Pause the game, hold L + R and press A, A, B, A, A, A, A, A.


Invincibility:
Pause the game, hold L + R and press B, B, B, A, A, A, A, A.


All weapons, items, keys:
Pause the game, hold L + R and press A, B, B, A, A, A, A, A.


Berserk mode:
Pause the game, hold L + R and press B, A, B, A, A, A, A, A.


Computer map:
Pause the game, hold L + R and press B, A, A, A, A, A, A, A.


Radiation suit:
Pause the game, hold L + R and press B, B, A, A, A, A, A, A.


Advance about 5 levels:
Pause the game, hold L + R and press A, B, A, A, B, B, A, A.


Tower Of Babel level:
Pause the game, hold L + R and press A, B, A, B, A, B, B, A.


Level Warp to "Tower of Babel:"
Pause the game, hold L + R and press A, B, A, A, B, B, A, A