The best kind of tip is that at the end of a colored marker. Except for money.
The Internet is a wonderful thing. It tells you what's in the news, gives you all of human knowledge at your fingertips, and most importantly lets you order pizza without talking to people, but then tells you the name of the human dispatched to bring you your large thick-crust extra-cheese. You can go a whole day on the Internet without talking to a single real human being except the one bringing you your pizza, and to be honest if you're ordering from Dominos.com the odds are not terrible that that's true — so why not do something special for the living, breathing soul who has come to bring you sustinence. He's special.