Rugby! First off because those guys hit like motherf*ckers not to mention taking hits, and they're athletic powerhouses with a mad threshold for pain. They're not stiff musclebound bodybuilders. Those guys can seriously move on the field. It could translate very well to MMA with a couple years of training. Heck if Tim Sylvia and Brett Rogers, a respective bouncer and tire changer, could have as much success as they did in MMA, then I'd give many elite level athletes like Rugby players damn good chances providing that they were to take MMA seriously. They already physically and athletically fit the part.
Taking out other combat sports makes this tough to answer. This may sound weird, but the one that makes the most sense to me are gymnasts. They tend to be freakishly strong, and their flexibility would be great for BJJ. But after typing that, I'm not sure if there is a professional gymnastics circuit. TFK
