Hahahahaha. Just kidding. Definitely have Fedor in there. Gotta go with Big Nog, and I'm gonna throw Mir in there because he essentially has overcome some big odds and had some great victories. I believe he has the most submissions for a HW in UFC.
Nog b/c his peak lasted longer and was more consistent. He went 7 years beating everyone not named Fedor. Plus Werdum's Strikeforce performance against Overeem and his fight against Andre Arvloski still leave some bitterness.