I would swear on the grave of my parents that I've never cheated at pool, but that doesn't mean I haven't been subjected to it. Each of the following happened to me:
Putting the Game Up Twice
There was an opponent of mine that would win a game, move a bead, take a bathroom break, and then come back and move another bead. Until I took exception, he would get away with it.
Shooting After a Dry Break
There was an opponent of mine that, in a tournament, opened the match with a dry break, but continued shooting. After he made the one and the two, I noticed that all the other balls were still on the table. He ran out. In the next rack, he broke dry again, and again tried to continue shooting, but this time I took exception.
Some opponents need to be watched!