To activate a cheat code type T then enter a cheat code, you'll see a message if you typed if correctly

Code Description
EXCALIBUR all weapons
SMALLROCKS unlimited ammo
SWALLOW fuel refill
UNLADENSWALLOW unlimited fuel
RABBIT full shields
ANTIOCH kills all opponents in the current levelI
GOTBETTER full health
KNIGHT god mode on/off
CAMELOT finish the level
DEBUG debug info
VERSION version number
GIMMESOMESUGARBABY all weapons/items
SHRUBBERY all items
RUNAWAY fires off all weapons
COCONUTS switch between movement modes
ALREADYGOTONE Message: "The World Is Now Your Oyster"