So basically just Type in game like in Doom,
heres the list

Nbreflect - mirror mode (cannot be toggled off).
Nbponcho - toggles the Lava Suit powerup for 300 seconds.
Nbkfa - gives the player full health as well as all keys, weapons, and ammo.
Nbkeys - gives the player all keys.
Nbdeity - toggles god mode, however the player can still lose health bonuses from damage.
Nbff - doubles fire speed similar to the Fast Fire Totem. Stacks similarly to the Fast Fire Totem and will be lost upon picking up a Fast Fire Totem.
Nbregularfingers - sets fire speed up back to normal.
Nbhot - toggles the Serum of Blistering Heat powerup.
Nbspoder - toggles the Climbing Thing powerup for 300 seconds.
Nbshooters - gives the player all weapons.
Nbdeathless - gives the player full health and morale.
Nbfrog - increases jump height by .1 each time it's typed.
Nbman - resets jumping height to normal.
Nbwoohoo - toggles slowly motion mode.
Nbgotta - doubles movement speed. This also affects falling and using Blows.
Nbufo - allows the player to fly via the spacebar.
Nbullets

and yeah Thats about it
have fun cheating you freak >:(