Press ~ during game play to display the console window. 
Type one of the following codes, then press [Enter].

Result                                Password
------------------------------------------------
Suicide                             - selfdestruct
Set gravity; default is -1400       - setgravity [number]
Additional cheats at pause menu     - enablecheats 
Blitz has full health               - givehealth
Blitz dances                        - dance
NOED opens its mouth                - hurtnoed
Invincibility and weapons/upgrades  - cheatdeath
(with 0 to 9)