I had pretty good 2 to 8 curveballs in Babe Ruth, then my Fresh. year in High School I found I could throw the 12 to 6 pretty good. Only used it a few times, once was the 3rd strike for a K though. The umpire's, batter's and my catcher's eyes were as wide as plates when I threw that.
I did have one time though where I threw an 2-8 curve and this kid swung so hard, he completely spun around and fell on the ground. I was busting up laughing on that one.
Then, around my Jr. year, my 12-6 decided not to work and from then on, it was 2-8, and 3-9 and a couple 3-6's.
There was one game where I threw almost nothing but curveballs, my hurt fuckin hurt after that. But usually throwing 100 or so pitches in a game hurt worse than that. Hell, when I threw 140pitches in one game, it didnt even hurt.