Apparently Roy Williams, Wide Receiver for the Detroit Lions, made the news a few weeks ago in a radio interview, stating that he had a no tipping policy. You can read about it in the Detroit Free Press. After his interview, he says, he was stopped at a red light and got into a conversation with the pizza driver, who told Roy how much he should be tipping.
This story in the same paper the next week describes how Roy then actulally did order pizza and paid a $20 for his $13+ order, leaving a generous $6+ tip.
I'm not sure I believe it, especially the part about the red-light conversation, but it does make some interesting reading.