the only cheat that has been found so far is right(2), left, down, up(3) and down. That is to unlock the body surf ability wich is a good jump move, it is a one hit kill to humans (not super soldiers),and normal infected.
No, but there are certain glitches such as multiplying items, walking on paintbrushes to get to high places, etc. If you want to know how to do those things then read the rest of my passage. In order...