Sidious in particular is high up on the list, since he followed Machiavelli's one line about a ruler appearing just but not ruling justly. He felt power itself was means enough to use absolute power. Also, Machiavelli felt fear and the occassional means of force can and should be used by his famed Prince.
Dooku himself wasn't a ruler, and Revan was a general, not a ruler either. Next in line would be Ragnos, who shrewdly and effectively ruled an entire Sith Empire for over a hundred years. We can only imagine how Machiavellan he was at heart. Very practical.
I'm not mentioning anyone from KoToR II
1) Sidious of course
2) Ragnos
3) Bane
4) Nadd
5) Sadow
6) Malak--maybe Revan as well
7) Kun
8) Vader--for his bombing of Xizor's city just to contain a plague.
9) Kressh--to a degree
10) I'm out of people, so, Dooku.
But Dooku was just a pawn of Sidious, so he's not really THAT Machiavellian.
Palpatine is easily the most Machiavellian Sith Lord. Dear ol' Niccolo describes in 'The Prince' that it is excusable to use ruthless tactics to acquire - and maintain - power. Palpatine clearly does this better than anyone else, and his methods are very much like Machiavelli's own.
Traya is a second.