The knuckleball is baseball's closest thing to a sideshow pitch, but it's no laughing matter for hitters. It's the sport's slowest pitch, but, paradoxically, CAN be one of the toughest to hit. The pitch is thrown with an odd grip -- with little in the way of rotation -- and the net result is a ball that flutters all over the place on its way to the plate. It can move side to side or maybe it will dip, or maybe ... who the heck knows! No one really has any idea where exactly the knuckleball is going to end up, not even the pitcher! Hitters find that swinging at knuckleballs can mess with their timing, sometimes for days afterward.
The downside to being a knuckleballer (and there are very few artisans of this particular craft; the simple-looking pitch is incredibly difficult to master) is that when it's not working well -- when a knuckleballer isn't "on" -- it's going to be a long night for said knuckleballer and his teammates playing defense behind him. That's because a knuckleball, when thrown poorly, without enough zany movement, is just a big giant beach ball to the opposing hitter, turning even the worst major league hitter into the most unfair ringer in a Sunday slow-pitch softball game.
Seen here is Toronto Blue Jay R.A. Dickey, who won pitching's coveted Cy Young Award in 2012 as a knuckleballer with the New York Mets. Note how his index and middle fingers touch the ball, arched high with the fingernails touching the ball. That's his knuckleball grip.