The Exile, by far. Revan was cool, but the Exile is such a complex and interesting character. He isn't a Jedi, but he hasn't falen to the Dark Side. I believe a silver lightsaber ingame signifies well this neutrality. He is hostile towards the Jedi Order, but he isn't a Sith. So intriguing. He is a great character, and even though Revan could wipe the floor with him in battle, Revan is either good or evil, through and through, making for a rather two-dimensional character. The Exile is great because his very rebellious nature is so unlike that of the Jedi Knights, and he wasn't afraid to disobey his masters to do hat he thought was right.
The Dark Lord