Enter the following codes at the Password screen under Options. To activate, go to the Bonus screen:

BENGAL	Invincibility
DISCUS	Infinite Ammo
CICHLID	Achilles Head mode
GOURAMI	Bullet Shield mode
PLECO	Silver Bullet mode
MOOR	Rubber Grenades mode
ZEBRA	Invisible Soldiers mode
TETRA	Men with hats
LOACH	All replay items

Thanks to Revolution readers Hool, John J. and Martin Brodeur!