Let's see- slow, no moves, no shot, no elevation, moderate hustle. I guess no one. Of course, I'm in my fifties, so maybe Antoine. Sorry, couldn't help myself, don't get upset guys, it was just a joke.
How about Rick Barry, because when I played, you could still take underhand foul shots, even though it was pretty dorky even then. Seriously though, some of the really bad foul shooters in the NBA ought to try underhand, but I suppose it would take some serious guts to be the only one doing it.