Unlock All Cinematics
     At the DOS Prompt and in your QuakeIII Directory, type:

quake3.exe +seta g_spVideos "\tier1\1\tier2\2\tier3\3\tier4\4\tier5\
5\tier6\6\tier7\7\tier8\8"

Various Cheats
     During  gameplay,  bring  down  the  console and enter any of the
following "Codes":

Code                    Effect
/iamacheater            Unlock All Levels at Skill 1
/iamamonkey             Unlock All Levels at Skill 100
/god                    God Mode
/give (item)            Give (item) (item names below)
/model                  sarge/krusade Hidden Sarge Skin

Item Names
all
ammo
armor
battle suit
bfg10k
flight
gauntlet
grappling hook
grenade launcher
haste
health
invisibility
lightning gun
machinegun
medkit
personal teleporter
plasma gun
quad damage
railgun
regeneration
rocket launcher
shotgun