I was surprised to see that the knuckleball isn't used very much. Since I used to try and practice it in my backyard when I was little (butchered it) I figured it was a normal pitch. I also learned that it's less hard on the arm and lets pitchers get in more throws and helps extend their career.
The movie follows two "knuckleballers", Tim Wakefield and R.A. Dickey during the 2011 season. The movie details the struggles that go into the pitch and the perseverance and dedication they put into perfecting the pitch.
It's a bit long for a documentary but I found it enjoyable to watch.