Go to the skirmish level selection menu. Hold
[Left Ctrl] + [Right Alt] + [Page Up] for about
one second. Go back to the main menu, and then go
to 'Arm Center'. You should have every part and
weapon available. Note: This also unlocks every
level and round in skirmish mode.
Press [Enter] during game play, type give me a big
head, then press [Enter] again. To return to normal
size, press [Enter] during game play, type get my
head back, then press [Enter] again.