In-game just press 'T' and then enter the following
codes:
mpimyourfather -- God Mode
mpwegotdeathstar -- Infinite Ammo
mpkingoftehmonstars -- All Weapons & Full Ammo
mpmaphole -- Complete Mission
mpdrdentz -- Full Health
mpwonderbra -- Full Armor
mpyoulooklikeyouneedamonkey -- Add All Armor Options
mpgoattech -- All Weapon Upgrades
mpmiked -- Exit Game
mpbuild -- Show Game Build
mpasscam -- 3rd Person View
mprosebud -- Spawn Snowtruck