Cheat Codes
Enter these on the passcode screen:

TUSKFISH - Unlock All Missions
BANNER - Invincibility
WRASSE - Bullet Shield
JAWFISH - Unlimited Ammo
BATFISH - Silver Bullet
CARDINAL - Achilles Head
BOXFISH - All Replay Items
PARROT - Invisible Soldiers
DOTTYBACK - Men With Hats
BETTA - Rubber Grenades

Yomashita Gold: Entrenchment tool
During the mission, you will find a Buddha statue sitting Indian-style holding a lotus flower. Approach it and you will take it.Near the end of the mission, after you save the pilot, go to the end of the hall and place the lotus in the fountain in front of the Buddha lying down. A message stating 'You have achieved enlightenment' will appear.The fountain will lower and a door will open to your right, Indiana Jones style with a great earthquake. Take the shovel inside and a message stating 'You have the entrenching tool'will appear.You can now load and switch your weapons much faster for the remainder of the game.