This cheat work when you have the 1.1 patch installed. While on the main screen type in (while holding shift) ''iwillcheat'' then one of the various cheats listed below:-

quickload - Load your saved game.
nohits - no damage to you.
goodhealth - Maximum life.
openalldoor - All doors are now open.
allitems - gives all items.
killthemall - kills all enemies/civilians.
showtheend - Skip to the end of the game.
gamedone - Win current mission.
gamefail - Fail current mission.
resurrect - Resurrect all team members.
funnyhead - Big heads on men.
enemyf - Skip to enemy view.
debugdrawwire - Wireframe.
playercoords - Your position
laracroft - change for your men

Note: Most of the cheats can only be enabled on the original unpatched game. The v1.1 patch will disable the cheats. At any opening screen or menu, type "iamcheater" or "iwillcheat" to enable cheat mode. If you entered the code correctly, you will hear a clicking sound. Note: The code may need to be entered twice in succession.

Then while playing the 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

Toggle invincibility cantdie
Invincible to gunfire nohits
Full health goodhealth
All weapons with full ammo allloot
All items allitems
Open all doors openalldoor
Kill all opponents killthemall
Current mission ends in failure gamefail
Current mission ends successfully gamedone
Revive fallen companion, except after drowning resurrect
Alternate uniforms, including dressing as Lara Croft laracroft
Enemy view from the front enemyf
Enemy view from the back enemyb
Show coordinates in top left corner playercoords
Big head mode funnyhead
Wire frame mode debugdrawwire
Load saved game of current mission quickload
View ending sequence showtheend

Cheat Codes (demo version)  -  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 the 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