Axis Arena

Unlocks every levels and rounds in skirmish mode and all weapon parts:
Go to the skirmish level selection menu.
Hold [Left Ctrl] + [Right Alt] + [Page Up] keys for about one second
on your keyboard. Return to the main menu, and then go to "Arm Center".

Big head size:
While playing with Axis Arena, hit [Enter], then type "give me a big head",
then hit [Enter] again.

Normal head size:
To restore the normal head size, hit [Enter] while playing, then
type "get my head back", then hit [Enter] again.