My two big bugbears are playing people who take nearly 45 seconds to play a shot - any shot. I mean hitting the ball off the tee for par 4s and 5s should be doable in 15 seconds tops - maybe 20 if there is a very strong cross wind. Likewise second shots on par 5s where you aren't going to reach the green.
Even most approach shots don't need constipation levels of delay surely?
My second bugbear are the players shooting ridiculously low scores on tournaments. I haven't worked out how this is done, but it clearly isn't by playing the game fairly.