Cheat mode:
Right click on the game's shortcut, select 'Properties' and add +set ui_console 1 +set cheats 1 to the 'Target' line. Now start the game. During play, press the ~ key to bring down the console and enter the following:

god                God mode

give all           All weapons

give [name]        Spawn specific weapon

health 100         Gain 100 health

noclip             No clipping

notarget           Invisibility

maplist            Lists maps

modellist          Lists models 

shaderlist         Lists shaders

record             Record game

kill               Suicide

devmap[name]       Load multiplayer map. Use the following for [name]:

dm_attrexian1

dm_borgurvish

dm_brigwad

dm_ctf_station

dm_guille

dm_idryll2

dm_kirk

dm_kw

dm_quarterdeck

dm_sewer

dm_t2_new

dm_t4mobius

dm_trophonius

   

   

Thanks to Revolution readers RedStar and Brody!