What Form Of Cheating Do You Hate The Most?

On Tuesday night, Rays pitcher Joel Peralta was ejected from the game against the Washington Nationals for having pine tar on his glove. However, this kind of cheating hasn't had nearly as much publicity as if someone had been caught using PED's. That begs to question, excluding Performance-Enhancing Drugs, what form of cheating in sports do you dislike the most?