God Mode:

During gameplay pause the game, then hold R and L and press A, A, B, A, A, A, A, A.

All weapons, keys, Items:

During gameplay pause the game, then hold R and L and press A, B, B, A, A, A, A, A.

Level Skip:

If you are totally stuck on a level, then use this cheat to skip it all together. Pause the game, hold L + R and press A, B, A, A, B, B, B, and then A. The word loading will appear if you got it right.

Invincibility:

During gameplay pause the game, then hold R and L and press B, B, B, A, A, A, A, A.

Computer Map:

During gameplay pause the game, then hold R and L and press B, A, A, A, A, A, A, A.

Berserk Mode:

During gameplay pause the game, then hold R and L and press B, A, B, A, A, A, A, A.

Radiation Suit:

During gameplay pause the game, then hold R and L and press B, B, A, A, A, A, A, A.