He handed the guy his pizza and the credit card slip and made sure to point out TWICE in less than 20 seconds where the place to leave a tip on the slip was. Then, as the guy was filling out the slip, he reached over him and pointed to the tip space again. As the guy filled it in, he said "Yes, that is my tip."
Every third word from his mouth was tip, it seemed. I'm all for tipping a delivery driver and a server and whatnot, but that was just rude and would have resulted in a curt "Thanks for the pizza" and a full view of my back as I walked away after leaving him a fat $0.00 in the slot he found it so necessary to point out for me.