Press T then enter one of the following codes

health Max Health
armor Max Armor
maphole Skip Level
pos Show position
skillz Get Skillponts Levels 3-4
poltergeist Be invisible
kfa get weapons, ammo, armor & health
mods Get silencer, scope & camera zoom
god Invincibility
build Show version
baddaboom ?????
guns Get All guns
ammo Max Ammo

Registry Cheat

Make a backup First!

From the start menu pick run then type in REGEDIT and move to the key:

[HKEY_LOCAL_MACHINE\SOFTWARE\Monolith Productions\No One Lives Forever 2\1.0]

Change the value of "EndGame" to 1.