I bet that's a fun experience when you ask them to remove it.
I'm pretty random when it comes to tipping. I think most of the time that randomness has me over-tipping a bit, but I can live with that. There is one pizza guy around here though that I'll go out of my way to give the smallest tip possible. I ordered a pizza online one day and paid the tip ahead of time on my credit card. They screwed up the order and delivered the wrong pizza. When the guy came back the second time he expected a second tip. He even went as far as to say "what, no tip?". Any time those words are uttered, you might as well kiss that money goodbye. Well, that and refusing to leave until he gets one doesn't go over too well either. I wonder how long he stood outside staring at my door. And yes, I realize the error wasn't his, but there's no way I'm going to pay twice. Luckily the pizza was kind of cold, so I can in fact blame that guy for something.