At the campaign selection screen that appears after the opening sequence, type "unlockcheatmode" to enable cheat mode. If you entered the code correctly, you will hear a clicking sound. Then while playing a game or at any menu screen, enter one of the following codes to activate the corresponding cheat function. If you entered the code correctly, you will hear a clicking sound.
Result
Cheat Code
Invincible, except for high falls noplayerhits
All weapons allammo
More resistance to gunfire goodhealth
Open all doors openalldoor
Kill all enemies killthemall
Return as zombie after being killed zombie
Current mission ends successfully missiondone
Current mission ends in failure missionfail
View ending sequence showtheend
Alternate uniforms, including dressing as Lara Croft laracroft
Enemy view from the front enemylookf
Enemy view from the back enemylookb
Show coordinates in top left corner playercoords
Big head mode bighead