AMOK

Level select:
Enter ZZZCYX as a password. A new "Level Select" option will appear at the top of the options menu.
Information in this section was contributed by Kenshin.

Invincibility:
Enter XBABYX as a password. The word "Correct" will confirm correct password entry. You will lose energy, but no lives, during game play.
Information in this section was contributed by Kenshin.

Rapid fire:
Enter YAYAYA as a password. Your mini-gun will have very rapid fire and will not run out of ammunition.
Information in this section was contributed by Kenshin.

Bonus mission:
Move south after completing the objectives in mission 1, phase 2. Enter the alternate exit in the dead end canyon to start a bonus underwater mission.