All Cheats:
Press ` in game to bring down the console, or press TAB for the quick
console. Then type one of the following commands:

God - Toggle God Mode
Amphibious - Underwater Breathing
Fly - Fly Mode
Ghost - Walk through walls
Walk - Return walking to normal
Invisible <bool> - Turn inivisibility on or off (true / false)
Teleport - Teleport to where your crosshair is pointing
AllAmmo - Full ammo on all possessed weapons
Allweapons - Give all weapons
Loaded - Give all weapons and full ammo on them (combo of
allammo and allweapons
SkipMatch - Win the current match and advance on the ladder
JumpMatch <int> -Jump to a specific match on the ladder, where <int> is a number. For example 43 for ladder 4, rung 3
ChangeSize <float> - Change the player size by factor # (i.e. 0.25 or 2.0)
LockCamera - Toggle locking the camera in its current position
FreeCamera <bool> - Delink the camera rotation from the actor
ViewSelf <bool> - Reset the camera to view the player (true to be quiet, false to have sound)
ViewBot - Cycle the camera through the viewable bots
ViewFlag - View the actor current carrying the flag
ViewPlayer <string> - Change the camera view to the given player
ViewActor <string> - Change the camera view to the given actor
ViewClass <string> - Change the camera view to the given class
KillViewedActor - Kill the actor the camera is currently viewing. Do NOT kill yourself! (Game will get stuck)
Avatar <string> - Possess a pawn of the given class
Summon <string> - Summon the given object
SetCameraDist <float> - Set the distance the camera has from its target
SetGravity <float> - Change gravitional pull
SetJumpZ <float> - Change Jump height
SetSpeed <float> - Mutiply the Player water and ground speed with the given value
ListDynamicActors - Output all dynamic actors to the log file
FreezeFrame <float> - Pause the game for the given duration
SetFogR <float> - Set red color component of fog
SetFogG <float> - Set green color component of fog
SetFogB <float> - Set blue color component of fog
SetFlash <float> - Set the duration a screen flash takes to fade away
CauseEvent <string> - Trigger the given event
LogSciptedSequences - Toggle logging for all scripted sequences
KillPawns - Kill all actor pawns except the player
KillAll <string> - Kill everything of the given class,
i.e. KillAll Pawn
KillAllPawns <string> - Kill all pawns of the given class
PlayersOnly - Toggle the level to a players only level
CheatView <string> - Toggle to view to the given actor
WriteToLog - Write the string 'NOW!' to the game log
ReviewJumpSpots <str> - Test jumping, the parameter can be 'Transloc', 'Jump', 'Combo' or 'LowGrav'.

Unlock All Skins:
Edit the file UT2003.ini (Located in your game system directory) with notepad and add the following lines to the end

[XInterface.Tab_PlayerSettings]
bUnlocked=True
bTDMUnlocked=True
bDOMUnlocked=True
bCTFUnlocked=True
bBRUnlocked=True

Beta Version Cheats:
In a single player game press TAB to get the console and enter a code below

allammo - Max ammo

god - Invincibility

loaded - Get all weapons

fly - flying mode

ghost - no clipping mode

walk - Disables flying and no clipping modes