The pitch is called the Gyroball. It's the subject of a book called, translated from the Japanese, "The Secret of the Miracle Pitch." And no one knows if anyone actually throws it.
It's all the topic of an outstanding feature by Yahoo's Jeff Passan, which tracks the history and mythology of the pitch that supposedly is unhittable.
The concept of the gyroball was perfected in a supercomputer by two Japanese scientists named Ryutaro Himeno and Kazushi Tezuka. In simulations, they showed how a pitcher with good mechanics could throw the baseball in a way that it spun like a bullet or, in sporting sense, like a perfect football spiral and broke like nothing anyone has ever seen. ... "A good gyro is impossible to hit," says Baseball Prospectus' Will Carroll. "Even if you did hit it, you can't do anything with it. If you're lucky you're going to aim the sweet spot of the bat on it and hit it off the end."
This whole thing sounds a little Sidd Finch-ish to us, since no one can locate anyone who actually throws the pitch (one Japanese pitcher has reportedly thrown in, but never in competition), but we love the idea of a phantom pitch out there that turns everybody into Ben Grieve. We bet Bugs Bunny knows how to throw that.
Searching For Baseball's Bigfoot [Yahoo Sports]