In Star Wars: The Force Unleashed 2 for the PS3, Xbox 360, and Wii, you can unlock the Sith Stalker Armor costume if you want to look a little more evil.
All you need to do is have a saved game from the original Star Wars: The Force Unleashed game that has viewed the dark side ending, and it will unlock automatically.
Pause the game and select Costumes to choose a different costume.