Infinite Ammo
     Pause  gameplay  and  press  Circle,  L2, Square, L1, Select, R2,
Triangle, Select.

Invincibility
     Pause  gameplay  and  press Square, L1, Circle, R1, Triangle, L2,
Select, R2.

Various Cheats
     At the Enigma Machine, enter any of the following "Codes":

Code                    Effect 
MONKEY                  Win Current Mission with a Gold Star 
ORANGUSTAN              Mission 2 
BABOON                  Mission 3 
CHIMP                   Mission 4 
LEMUR                   Mission 5
GORILLA                 Mission 6
WHATYOUGET              Silver Bullet Mode 
BULLETZAP               Bullet Shield Mode 
HABRDASHR               Men with Hats 
BACKSTAGEO              Making of D-Day FMV Sequence 
BACKSTAGER              Making of Needle In A Hay Stack FMV Sequence 
BACKSTAGEF              Making of Several Bridges Too Far FMV Sequence 
BAGESTAGES              Making of The Horten's Nest FMV Sequence 
TIMEWARP                Complete Previous Mission with Gold Star 
BOING                   Rubber Grenade Mode 
LONGSHOT                Snipe-O-Rama Mode 
URTHEMAN                Perfectionist 
GLASSJAW                Achilles' Head Mode 
WHERERU                 Invisible Enemies