This is just pure fantasy and for fun but if you put Mighty Mo, David Tua, Mark Hunt, Butterbean, Kimbo Slice, Cheick Kongo, Sergei Kharitonov and Alexander Emelianenko in a oldschool UFC 8 man tournament, who would take it.
Depending on the card layout of course I could see it boiling down to Emelianenko vs Tua and I'm sure I'm going to get some flaming for this but I would go with David Tua.
First of all, you are crazy. I have no idea who would win this tournament, and I don't even have a good guess. But wait...that doesnt' mean I don't have a guess. I'm going with Kongo.
Aleks and Hunt in the final.
50/50 Hunt via KO or Aleks via sub
Tua vs. Hunt would be good.