Kill Your Buddy
In a 2 player game or VS. mode, hold the right trigger and press A, B, X, and Y simultaneously to toggle the cheat on or off. This enables you to hurt your partner if in a 2 player game. If in VS. mode you will both be invincible till toggled off.
Secret Background
In the 1st level of the game, go to the conveyor belt and kill the droid riding it and then you'll see a nice colored background.
Points needed per level for maximum experience
Level - Points
1 - 24000
2 - 21000
3 - 31500
4 - 39000
5 - 34000
6 - 51000
7 - 30000
8 - 7650
9 - 14000
10 - 12000
Ultimate Saber
In level 14, fight 100 opponents, including all the troop types from the game to unlock the Ultimate Saber. The Ultimate Saber enables one-hit kills on all enemy characters excluding Bosses. You can turn it on or off in menu that appears when the game is paused.
Note: You only need to get it once with one of the characters for all characters in that mode (one or two player) to be able to use it.
Level 14: Survival Challenge
Successfully complete the game with Mace Windu.
Level 13: Gungan Round-up
The Gungan Round-up level is accessed by finding the three Gungan artifacts throughout the game. They are in the following locations:
Naboo Swamp
Near the end of the second level down in crevice.
Tatooine
On a medium size plateau up against the screen. Jump forward in a leap of faith. It is inside the hut with the Jawa in front of it.
Gungan Ruins
Near the end after the covered trap, right next to a tree and a large patch of bushes.
Level 12: Kaadu Race
Successfully complete the game with Adi Gallia.
Level 11: Droidekas
Successfully complete the game with Plo Koon.
Defeating the game (without defeating Darth Maul)
When you reach Darth Maul fight him for a little bit then quit the game without beating him. When you go to the Character Selection screen Darth Maul should be a couple characters down.
Bounce droids fire back to it
When Fighting a droid, or any other, let them fire at you but when the bullet is about to hit you, press: "Block" or "L". It will bounce off your saber back to the droids.
Note this cheat will not work on the following:
Rifle Droid
Green Droid
Flame Droid
Loader Droid
or any force