Everything MMA-related goes here.
K-1 and boxing, and more obscure sports like Kyokushin, Daido-Juku competition is also allowed.
OK, I'll start.
I believe Fedor Emelianenko is the greatest fighter in the world, of all time.
[YOUTUBE="http://www.youtube.com/watch?v=lVVrNOQtlzY"]Fedor "The Last Emperor" Emelianenko[/YOUTUBE]
However, my favorite combat sport has got to be K-1 MAX, which is the 75kg division of K-1. The heavyweights are fun to watch, but I don't think they are anywhere near the technical level of the smaller weightclasses.
The best standup/Muay Thai fighter in the world today:
[YOUTUBE="http://www.youtube.com/watch?v=6jm5cJ-OyO0"]Yodsanklai "The Computer Wizard" Fairtex[/YOUTUBE]