Nice thread on the UG. Let's do it here.
Here's a list of candidates:
Fedor Emelianenko
Bas Rutten
Don Frye
Ramage Jackson
Wanderlai Silva
Vitor Belfort
Roger Huerta
Mirko Cro Cop
Tank Abbott
Marco Ruas
Antonio Noguiera
Frank Shamrock
Ken Shamrock
Mark Coleman
Jens Pulver
.....and just for the sake of pure ferocity and punching power, lets also include Marciano, Tyson, Duran, Hearns, Pryor, Foreman, and Dempsey.
What say you guys?