Cheat: Item Duplication

Go to Manaan and down into the underwater facility. Equip your teammates with the armor and accessories that you want to duplicate and save(very important)right in front of one of the pressurised door.

Now, unequip all of the things you want duplicated from your teammates and go into the pressurised door.Go right back in and you will notice that your teammates' equipment are back on. And more importantly, you will notice that there is a duplicate of each item added to your inventory. You can do this as many times as you want, and as far as I know, it causes absolutely no problems. It's your choice to keep it, or sell it for big bucks.

Also note that when you duplicate an upgraded weapon, all the items that are in it are duplicated too. So, you don't have to worry about things like evenly distributing crystals to all of your jedis lightsabers. Just make your best lightsaber, and duplicate it.

Cheat: Voice Change
With your primary controller plugged into the first port, plug a second controller into the fourth port. At any time, you can use the second controller to change the pitch of the voice acting.
Black Button: Lower pitch (Barry White)
White Button: High pitch (like Michael Jackson)

Unlockable: Earn Different Endings
Finish game on the Light Side (by doing good deeds and denying the Dark Side) to see the Light Side ending. Finish game on the Dark Side (by doing evil and accepting the Dark path) to see the Dark Side ending.

Hint: Extra Items

On the Ebon Hawk, talk to each member of your crew. You can ask each one to make you specific items: