To use these codes, just type them in at the console.
(Press the ~ key to get to the console)
GOD God Mode
NOCLIP No Clipping Mode
IMPULSE 9 All Weapons and Keys
IMPULSE 255 Quad Damage
GIVE # Gives any # gun
GIVE R # Get Rockets
GIVE N # Get Nails
GIVE H # Get Health
GIVE S # Get Shells
GIVE C # Get Cells
KILL Suicide
FLY Fly Mode
MAP E#M# Level Warp
NOTARGET Enemies Won't See You