A year or two ago, I was playing in my country's national 8-ball event, final 8, race to 8, against a notorious slow player, a former billiard and snooker pro, who has held world records for the longest snooker matches in history, and many players believe he delays game outcomes as a deliberate strategy to put his opponents off their games.
I got the 1 minute clock on him after about 4 games. This didn't help. He'd take 45 seconds on the simplest of shots and cluster up balls and snooker at every opportunity, not to mention taking a couple of toilet breaks, during which it seemed he had time to take a shower and change.
After getting to a good early lead, I began to try to accelerate the games, perhaps taking on some higher risk shots than I otherwise would. After 2.5 hours, he crept to a 5-4 lead. All other games in the round had finished, some over an hour before.
This was not an experience I wanted to be a part of and I felt bad thinking players could be waiting on our game to finish for another 90 mins or so, some who had planes to catch that evening.
I quit the game then, not in anger, but for the reasons above, and in protest for the way in which my opponent plays outside the spirit of the game. There is generally a sigh of relief when he is knocked out of tournaments. I won't mention his name, because he is known to be litigious, and has successfully fought off attempts to have him banned from tournaments.