Press [T] before all codes for the text box:

knight                  Invincibility
gimmesomesugarbaby      All weapons and gear
excalibur               All weapons
shrubbery               All power-ups
rabbit                  Full shields
igotbetter              Full health
verysmallrocks          Unlimited ammo
smallrocks              Full ammo
unladenswallow          Unlimited gas
swallow                 Refuel gas
camelot                 End level
grail                   Get arena flag
alreadygotone           All arenas available
antioch                 Kill all enemies
runaway                 Fire all weapons
coconuts                Linear movement toggle