Enter these on the passcode screen:

BUTTERFLY - Unlocks All Missions 
TANG - "Bullet Shield" mode allows bullets will not damage you.
GOBY - Unlimitied Ammunition 
PUFFER - "Always Sniper" mode allows all guns to zoom like a sniper rifle
TRIGGER - "Invisible Soldiers" mode 
HOGFISH - "Perfectionist" mode 
DAMSEL - "Rubber Grenades" mode 
GARIBALDI - All Replay Items 
SPINEFOOT - Makes Everyone's Arms Huge 
SEAHORSE - Men With Hats 
TILEFISH - Silver Bullet Mode allows enemies to be killed with one shot
MANDARIN - "Achilles Head Mode" 
Japanese can only be killed with a headshot when this cheat is active

Control main menu:
Move the Right Analog-stick to control the background at the main menu. 

Search for 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.

Day Of Infamy: Unlimited ammo cheat: 
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. As you are making your way up through the ship you will see a 
soldier that has been sprayed in the face with steam from an exploded pipe. 
Approach the soldier and press X. The message "Entrenchment Tool Used" will 
appear. This will unlock the "Unlimited Ammo" cheat in the bonus menu. 

Multi-player skins:
If you receive a medal for a mission, you also will receive a skeleton key which 
opens a small box which contains a new skin for multi-player mode. There is one 
box per mission with the exception of the Pearl Harbor mission.


Bridge on the River Kwai: Bonus objectives: 
Eliminate 10 enemies at checkpoint. Disable the dock. 

Day Of Infamy: Bonus objectives: 
Help the crewman shut the hatch. Save the crewman with the fire extinguisher.

Day Of Infamy: Hidden cheat:
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. Dig at a vent to find the cheat.

Day Of Infamy: Unlimited ammo cheat: 
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. As you are making your way up through the ship you will see a 
soldier that has been sprayed in the face with steam from an exploded pipe. 
Approach the soldier and press X. The message "Entrenchment Tool Used" will 
appear. This will unlock the "Unlimited Ammo" cheat in the bonus menu. 

Fall Of The Philippines: Bonus objectives: 
Find the gold Buddha. Find a picture of a Japanese general.

Fight For The Philippines: Bullet shield cheat:
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. Once you reach the baseball field, in one of the corners is a pile of 
dirt. Press X by it and you will unlock the "Bullet Shield" cheat in the bonus menu. 

In Search Of Yamashita's Gold: Bonus objectives:
Destroy the radio equipment. Destroy five sake water barrels.

In Search Of Yamashita's Gold: Entrenching 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.

Midnight Raid On Guadalcanal: Bonus objectives:
Find five pieces of intel, Blow up the generator. 

Midnight Raid On Guadalcanal: Hidden cheat:
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. Dig at the two sandbags blocking the entrance to a tunnel.

Midnight Raid On Guadalcanal: Silver bullet cheat:
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. There is a barn-like building with no walls in the mission. On one 
side of the building is an odd pile of dirt. A trench can be seen leading from the 
dirt, under the building and into a foxhole. Use the entrenching tool to dig out the 
dirt and unlock the "Silver bullet" cheat.

Pearl Harbor: Bonus objectives:
Shoot down 20 planes. Shoot down 75 planes.

Pistol Pete Showdown: Bonus objectives: 
Take over the howitzer. Save Lt. Harrison 
(press Action near him when he is on the last bridge).

Pistol Pete Showdown: Lt. Harrison multi-player skin:
The box with Lt. Harrison's skin for multi-player mode is at the outpost cabin 
where you find and rescue the Allied patrol and get Lt. Harrison to follow you. 

Pistol Pete Showdown: Saving Lt. Harrison:
Note: This trick requires the trenching tool or machete. Press Action on the bridge 
after blowing up the third artillery piece to save Harrison's life and get a bonus.

Pistol Pete Showdown: Machete replay item:
The machete replay item can be found at the outpost cabin where you find and 
rescue the Allied patrol and get Lt. Harrison to follow you. It is around behind the 
cabin in a small trench that leads under the building. The machete can be used to 
cut the vegetation in certain areas to gain access to hidden weapons and ammo 
caches. 

Pistol Pete Showdown: Men With Hats cheat:
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. Use the entrenching tool at the entrance to a save radio just past 
two Japanese machine gun bunkers to unlock the Men With Hats cheat.

Singapore Sling: Bonus objectives: 
Save three POWs. Find three pieces of intel.

Singapore Sling: Achilles' Head cheat: 
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. In the small staircase room that leads to a small indoor platform 
with a broken window and a catwalk leading to the industrial building (where the 
first POW is found), there is a silver air duct vent on the floor by the foot of the 
stairs. Press Action by it and the duct will disappear, unlocking the cheat.

Singapore Sling: Hidden cheat:
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. Dig at a vent to find the cheat.

Singapore Sling: Hidden health:
During this mission you have to meet a man. Go to the noodle bar. The bar has 
noodles on it which will give you health. 

Super Carrier Sabotage: Invulnerability cheat: 
Note: This trick requires the entrenching tool from the Search For Yamashita's 
Gold mission. Make your way through the mission until you reach a room with a 
row of lockers to the left of the entrance door. One of the lockers is shaded darker 
than the others. Press Action in front of it. A message will appear, stating that the 
entrenching tool was used and that the cheat is unlocked

Super Carrier Sabotage: Bonus objectives: 
Send the false radio signal. Find three pieces of Intel.