Cheatcodes:
Press " ` " (or tilde) to bring up the console:
TheTrooper ?- God Mode
SunandSteel -- Refill Ammo.
DieWithYourBootson -- All Ammo.
StillLife -- Invisilibility.
Revelations -- 8 Artillery shoots.
You should also try to enter this figure of speech: "you've got problems", just like it says here, and change to 3rd person view to see whats happens. Does not work with all versions though.