It's been around forever, and up until 1920 was actually legal. What isn't understood is that it's not real easy to throw, and if thrown improperly is often a gopher ball and winds up as a bleacher souvenir.

It falls into the ancient "it ain't cheatin' if you don't get caught" philosophy of most of this list, with scuffballs, creative groundskeeping, sign stealing, corked bats etc, but well below the steroids and betting end of the spectrum. There's other stuff, not on this list, like the phantom double play, which is in the same category.

A spitball is a ball that has some substance on it (like spit, or vaseline) which creates aerodynamic drag on the ball, which allows the ball to deviate from it's normal path. I wouldn't consider it a terrible offense, especially if it's just spit. .... the only pitch that I know of that doesn't spin is the knuckleball ...

There are those who argue that the spitball should be legalized again. . .the object is to throw a ball without spin by squeezing the ball out of your hands (am I right? I could use a little help here.. .) It is the pitching equivalent of a corked bat and thus should stay illegal.