If you press Ctrl-Alt-F4 at the same time, you get access to a nuke beacon which can destroy the entire base in one shot. 
If you put a small divot (no more than 1cm) above the "R" on the Data disc, you remove the section which has the ammo limits and clipping restrictions. 
If you curse in the WOL chat rooms, they email you a "cheats" code. 
If you plant a beacon with less than 50 seconds to go in the round, you automatically become MVP (don't NEED to spread this one around, as people already seem to believe it
) 