UFC Heavyweight Fighters
The top 'official' weight class in the UFC and other MMA organizations is the heavyweight division. Some promotions in Japan and elsewhere recognize a 'Super Heavyweight' class where there is no weight limit and there has been discussion in the US about creating such a weight class as fighters get bigger and heavier. Currently the heavyweight class has an upper limit of 265, with fighters weighing 205 or less usually competing as light heavyweights.
The current UFC heavyweight champion—and regarded by most as the top heavyweight in the world—is Cain Velasquez who before entering the professional MMA ranks was a standout collegiate wrestler at Arizona State University. Velasquez became UFC heavyweight champion via a first round knockout of former WWE superstar Brock Lesnar on October 23, 2010. He's scheduled to make his first title defense this fall against Junior Dos Santos in a matchup tentatively scheduled for November.
Brock Lesnar, the previous champion, was a very polarizing figure during his reign. Many neophyte MMA fans had issue with his background in pro wrestling, unaware that there have been countless competitors in the US and Japan that had some degree of experience in 'sports entertainment' including several UFC Hall of Famers (Ken Shamrock, Mark Coleman). Lesnar lost his first UFC fight, falling victim to a kneebar from Frank Mir, before winning his next four fights prior to his loss to Velasquez.
The fighter that most serious MMA experts consider the greatest heavyweight of all time, curiously enough, has never competed in the UFC. That would be Russian nightmare Fedor Emelianenko, who competed primarily in Japan during his prime. He also fought in a number of other organizations around the world including Strikeforce, BoDog Fight and Affliction's MMA promotion. After going most of his career undefeated Emelianenko is coming off of two consecutive losses and most observers think that his professional career is nearing an end.
There are a couple of current 'X factors' among top MMA heavyweights. Former UFC champion Josh Barnett left the promotion years ago on bad terms and became a huge star in Japan both as a pro wrestler and MMA competitor. He's continued to improve his game and is now one of the top heavyweights in the world though he hasn't competed in the UFC since his original departure from the promotion. He's currently contracted to the Strikeforce promotion which was recently purchased by UFC parent company Zuffa LLC. In addition, the reigning Strikeforce heavyweight champion Alistair Overeem is considered by many to be the most physically imposing fighter in the world. Overeem, who also competes in professional kickboxing, has spent most of his career competing in Japan an his native Holland. Both Barnett and Overeem would represent very intriguing opponents for UFC champion Velasquez.