If you want the best Star Wars Light Saber for your Jedi or Sith costume for Halloween or for just looking cool in front of your bedroom mirror, then these bad puppies are probably the best.
The Star Wars Force FX Light Sabers are available in 7 delicious flavors. They combine light and sound into a crescendo of Jedi coolness that you have to experience first hand to fully appreciate. As you can see you can get Count Dooku, Obi-Wan, Darth Vader, Darth Maul, Anakin, Yoda, and Asajj Ventress.
Check out all the specs here.
Here is a cool video of them in action. At first you think this might be pretty lame, oh no light saber cosplay, but it turns out to be pretty cool. Well done.
Word of Warning: BE CAREFUL with these! Don't go hog wild with your Light Saber and start slashing everything at random. Jedi to idiot with a broken Light Saber in 2 seconds. *sniff sniff* Damn you Darth Coffee Table!!!