Defeat a character in the Jedi Arena during game play to unlock him or her in versus mode.
All Levels
At the New Game screen, enter GREYTHERAT.
Battle Royal mission
Defeat Darth Maul in level 25 to unlock the Battle Royal mission, where you have to fight eight other Jedi Masters in the Saber Arena.
Chewbacca Body Shield
When you appear at the beginning of the first level, turn around and you'll see Chewie standing at the end of the walkway. Go up and press Y to talk to him. After that, he'll follow you around the level. When things get tough, he'll step in and take some of the blasts shot by the enemies. He roars a lot but I've yet to see him die from the damage.
Easy Jin'hah Defeat
On Secrets of Black Heth level an easy way to destroy them is to get them by a ledge and use Force Push (left trigger then y).
Easy way to kill Darth Maul
The only easy way to kill Darth Maul is to stay as far away from him as you can before he strikes down at you move out of the way when he does this and counter attack him with a force manuver of your own( mine is the turn spinning saber strike) hold r and use the analog stick. to beat the timer you have to be very good and know darth maul's weak points to kill him quickly.
Force Slow
Force Trigger + White Button = "Force Slow".
Open all levels with bonus levels
Make a new game called GREYTHERAT press enter then when you load the name every level will be open including the bonus levels.
Stay in slow motion
To stay in slow motion, all you have to do is, at the begining of a mission throw your light saber using force and while the light saber is still out ofr your hands go into slow motion. Once it starts to speed up again keep hold of force and keep pressing the slow motion button. If you have done this correctly you should stay in slow motion for the rest of that level. You will have to re-do it for each level. This is more a glitch than a cheat.
Unlocks all levels up to Darth Maul
Go to the main menu. Select New Game. Then type in M1A2U3L4!? That should unlock all levels up to Darth Maul.