Which Major League pitcher has thrown the nastiest breaking pitches you've ever seen? If you have video post, but otherwise just tell the pitcher.
For me, it would have to be Kerry Wood back when he was young and healthy. His curveball and slider were both just so unbelieveble, I can't throw stuff that nasty with a wiffle ball.
He throws some dirty curveballs near the beggining, and then check out the 1:19 atbat. That slider should be illegal.