Terminator 3: The Redemption Cheat List
Input these during the Credits Movie in the Main Menu section
* Invincible Mode: Circle + R2 + R1
* Upgrades: Circle + Triangle + L1
* Unlock Levels: Circle + R2 + Triangle
These cheats have been verified to only show up and not actually carry over into the actual gameplay session. The exceptions are Unlock Levels, which unlock all stages with a score of zero and Invincibility, which applies itself quite well to the Co-Op mode.