Unreal Tournament 3 Codes -

Unlock Characters
Enter the following codes at "Custom Character" screen:

phayder - Unlock Alanna (Necris)
jihan - Unlock Ariel (Iron Clad)

Unlock all characters in campaign
In addition to the two preorder characters (Alanna and Ariel), 8 more characters are unlocked via campaign on any difficulty. Note: To unlock Leaders (Lauren, Matrix, Scythe), be sure to choose all the second choices for missions in all chapters, and kill the Leader in every deathmatch with them. By the end of the chapter, they will be unlocked.

Akasha - Unlocked after final mission.
Damian - Unlocked after early mission in Chapter 4.
Kragoth - Unlocked after early mission in Chapter 4.
Lauren - Defeat in Deathmatch sidemission in Chapter 2.
Loque - Unlocked after CTF in Chapter 5.
Malakai - Unlocked after early mission in Chapter 4.
Matrix - Defeat in Deathmatch sidemission in Chapter 3.
Scythe - Defeat in Deathmatch sidemission in Chapter 4.