Press T then enter one of the following codes:

Effect-Code

All ammunition - ammo
All weapons - guns
All weapons, ammunition, health, armor - kfa
Full armor - armor
Full health - health
Get skillpoints (level 3-4) - skillz
God mode - god
Invisibility - poltergeist
Level completed - maphole
Level skip - nextmission
Scopes, silencer and camera zoom - mods
Show position - pos
Show version - build
Spawn snowmobile in snow levels - rosebud
Stronger explosions - baddaboom
Unlimited ammunition - tears