1.Exar Kun- the guy invented a new version of the light saber not to mention he almost destroyed the republic had it it not been for Ulic.
2. General Grevious -The dude is one of the only people with no force potential to kill a jedi with a light saber.
3. Revan- look at the KOTOR games enough said.
4. Anakin/Vader- he is an extremely powerful sith/jedi. If it wasn't for his character star wars would not be what it is today.
5.Darth Maul- Great combat form. Plus he got a nice costume.
6. Boba Fett- He is still mysterious plus I like the fact that he lets guns do the talking for him.
7.Yoda- one of the greatest jedi ever. love the way he talks, plus he stands tall over all.
8.Darth Nihilus-The guy destroyed/ate a planet. He feeds on the force in objects like jedi.
9. Darth Bane- PoD enough said.
10. Tulak Hord- I don't have good reason for why I like him, I just do plus to be called The great light saber duelist of his time which includes many powerful sith lords is saying something about him.