Spot Shots
Back in the 80s some guy came into our local poolroom asking if anyone wanted to shot spot shots for money. One of our best players took him up on it. I believe the rule was whoever missed payed the other guy (they played for either $20 or $50...I can't recall). You could only quit after your own shot. Our local guy, I believe, made 40-some consecutively before he quit (9' GC).
I used to practice spot shots. If you play a lot of one pocket, they come up a lot and they're almost always critical to winning or losing.