These are the UT2004 cheats and most of them should work in UT2004
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 Invisbility 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)
SetJumpZ <float> - Change Jump height
SetSpeed <float> - Mutiply the player water and ground speed with the given value
PlayersOnly - Toggle the level to a players only level
summon xweapons.rocketlauncherpickup - Get rocket launcher
summon xweapons.shieldgunpickup - get shield gun
summon xweapons.shockriflepickup - Get shock rifle
summon utclassic.classisniperriflepickup - get sniper rifle
Summon onslaught.ONSHoverTank - Get a Goliath
summon onslaught.ONSPRV - get a hellbender
summon xweapons.supershockriflepickup - get a instagib shock rifle
and others, If you want them ask for them at my mailadress: k0a0i7@hotmail.com