The Miami New-Times used some very scientific analysis to figure out who the worst celebrity tippers in America are. Two sports folks have showed up in the top ten and you're probably not terribly-surprised to find out it's Tiger Woods and LeBron James.
LeBron came in fourth overall and was cited for once allegedly leaving a $10 tip on an $800 bill. The incident took place in Cleveland, which basically makes the incident a giant metaphor for his time there.
Tiger strives to be the best in everything he does. So he must take some form of pride in being the No. 1 worst tipper around. Woods showed up on every list the New-Times cross-referenced and seems to have a reputation for tipping and then retracting said tip at a moment's notice.
So basically, if you're a waiter and the dinner party you're serving includes LeBron, Tiger and Jeremy Piven, don't even bother.