Frank Mir almost had it on Ian Freeman in the UFC back in the day (starting from top, not bottom). Then Frank Mir went out and pulled a Frank Mir.
A friend of mine wins with knee bar from bottom/side/top half all the time at black belt. It's funny to watch the matches because people don't see it coming. He's done it for years...I think he even has a video out on it lol!
His name is Ronnie Wuest.