Cain Velasquez and Junior dos Santos at UFC 155 doesn't qualify as a slugfest. For that to have been possible, dos Santos would have needed to, you know, do some slugging.
The heavyweight title fight is better described as a shellacking, a one-sided beating as bad as any I've ever seen in a high-level MMA fight. For 25 minutes, Velasquez pounded away at dos Santos. Perhaps it was karmic—after all, dos Santos once delivered a similar beating to poor Roy Nelson.
There have, however, been plenty of great heavyweight donnybrooks in MMA history. These are 10 of them. Whether they are the best 10 is open to dispute. Let me know what I missed in the comments.