As a child, I had a list of the top 5 wrestlers you wouldn't want to meet in a dark alley. Rick Steiner and Madusa Miceli were on the list, but for the life of me, I can't remember the other 3.
Just before The Benoit tragedy, we were sitting around thinking of names who would be legit bad asses in MMA. Chris Benoit was the first, followed by Elijah Burke and C.M. Punk. In Benoit's last televised match with Elijah, when things started to heat up, we thought if anyone could get himself out of a bad situation with Benoit, it would be Elijah.
As many have already noted, taking out the knees of some of the big guys would give you an immediate advantage and give you the chance to crack him in the skull (just saw this on L&O: Criminal Intent last night). And as everyone knows, if you're the smaller, faster guy you'll do fine, until the big guy catches you.
My current favorite monster right now is Brock Lesnar and I have to say my money's on him every time.
Edit: Just got off the phone with my sister who was both a soldier and a cop. She says that even though the Army and Police Academy both trainined her in hand-to-hand combat, in a lockerroom brawl or free for all fight, the training would not help very much as the others would probably not be fighting the same way.