Since we're also bringing up the worst things other people have done to us, I have a couple zingers.
I was gambling with this guy and I took a break to go to the washroom. I was up significantly. I can't remember why he was playing when I got back since I never take a break during a game, but only between games, but he was playing when I returned and I asked him what happened. He said he shot for me while I was gone and I missed, so now he was shooting!
Another time, when I was bearing down on a shot, he just THREW his stick down in front of me. He was a serious sharker!
Another time, I warned him that I had to go to work in another hour, so we would be quitting then. (I would go visit Mike and play pool in between when I worked 2 - 16 hour shifts at the VA Hospital. My kids were at their dad's.) I would work 16 hours on Saturday and instead of going home and sleeping in between, I would go to the Casino Club and play, then work another 16 hour shift.
When it got to be the witching hour, I told him I was quitting and he said, "Hey, you can't keep quitting me winner!" and I replied, "I can't stay long enough for you to win!"
But the worst thing that ever happened to me (other than getting called for my hair grazing a ball at World's) was done by a chick who lost all my respect and good will toward her.
She made a bad hit and hit the 8 before the 5. There was plenty of room to cut the 5 in, so I had never called a ref. I was out of my chair calling the foul (which was aimed at the pocket near my chair, btw, so I got a good look at it) before the balls stopped rolling and the position of the balls bore out the foul. She asked, "How is that a bad hit?" and I said because she hit the 8 first.
She said vehemently that she didn't foul. So you know how when someone is that vehement, you start questioning if you actually saw what you saw? Well, I looked down the entire row of sweators and they were all nodding their heads and confirming the foul. So I said she certainly had.
She said, "FINE, take ball in hand then!" and flounced back to her chair. Now later, a mutual friend of ours told me that she was shooting on the table behind us and she never saw the shot, but she did hear this chick saying that and she told her opponent that she wished ________wouldn't just give up ball in hand when she didn't think she fouled.
So since she was being so snotty (there were 2 other incidents that happened in that match!), I said , "Fine, I will!" and I picked up the cueball. No sooner are the words out of my mouth, when she turns around and says, "What are you doing?" I said, "I am taking ball in hand." She says, "I NEVER SAID YOU COULD HAVE BALL IN HAND!"

WTF!
So the ref/TD comes running over and asks what happened. I said, "She fouled, she said I could have ball in hand, so I took ball in hand." She says snottily, "I didn't foul, and I didn't say she could have ball in hand!" So the ref takes the ball out of MY hand and gives HER ball in hand!
Now our mutual friend had heard her telling me I could have BIH (as evidenced by her comment she made), as did everyone else. I have played in enough tournaments, pro and otherwise, to know to ask before picking up the cueball, but this one just flabbergasted me.
I had considered her to be a friend. She had emailed me pics of her new baby, dogs, husband, etc. and she just blew me away and I lost whatever respect I had for her. I bore down from there on out and finished the set without her winning another game. Un-fricking-believable!
I have absolutely no use for this lying sack of doo doo and will not speak to her to this day.