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

excalibur - all weapons

smallrocks - full ammo

verysmallrocks - neverending ammo

shrubbery - all gear (health kits, napalm, etc.)

swallow - full tank of gas

unladenswallow - bottomless tank of gas

rabbit - shields recharged

igotbetter - Health Recharged

knight - Invincible

coconuts - Linear Movement (Weird!)

grail - gives you the arena flag

camelot - conquers arena

gimmesomesugarbaby - all weapons and gear

alreadygotone - all arenas become available

antioch - kills all opponents