Enable cheats and press '~' (tilde) during gameplay to bring up the cheat console. Then enter the following case sensitive codes (without the quotes) to enable the corresponding effect.
Type '/g_gravity (0-800)'
Change View Angle:
Type '/cg_thirdpersonangle (-360-360)'
Change View Range:
Type '/cg_thirdpersonrange (320-500)'
Hidden Sarge Skin:
Type '/model sarge/krusade'
Press '~' (tilde) key to open the console and then type /svdevmap (map name) to load the level in Single Player mode then enter any of the following codes in the console to unlock the corresponding effect.
Unlock God Mode:
Unlock ALL Weapons and Ammo:
Unlock ALL Levels at Skill 1:
Unlock ALL Levels at Skill 100:
Unlock Hidden Skin:
/give (item name)
No Clip Mode:
/spdevmap (name of level)
This will make the fraglimit increase, so you can play for longer. Remember the space or it won't work.
Change Map In Game:
You will be able to change the map during gameplay if you type (without the quotes) '/Map' followed by a map name (eg '/Map Q3DM6').
Third Person View:
If you press '~' (tilde) key when cheats are enabled so you bring up the cheat console and then enter '/cg_thirdperson 1' (without the quotes) you will enable third person view.
Unlock ALL FMV Sequences:
Start a game with the quake3.exe +seta g_spVideos 'tier11tier22tier33tier44tier55tier66tier77tier88' command line.