edisoncarter has found a decent cheat, probably more useful for newbies I guess, since it gives you infinite health. There's also a cheat which we don't know the affect of, so please inform us if you find out.
Makes you mostly bulletproof, and fire, punches and melee attacks don't hurt you anymore. You can still be hurt by explosions, falling, getting run over, and drowning.
It is not currently known what this cheat actually does, please inform us if you find out
For all the cheats on one page click here.