I'm not sure how well MMA fighters would do against a good Krav Maga practitioner, that shit is hardcore. Though I would be inclined to say that most Military close quarters combat is focused on fighting with weapons. In an outright hand to hand fight the MMA fighter will most likely win.
Krav Maga is grossly overrated. I don't need to pay someone to tell me how to kicks somebody in the testicles. (Ouch).
I doubt ANY MMA fighter (besides Fedor and Lesnar) could beat a prime Mike Tyson. The guy was too fxcking crazy for almost anyone to handle.
Actually, many fighters could, if they took it to the ground. That's whats so great about MMA. The fight (unlike boxing) can take place anywhere.