One local-ish place to us has specials every once in a while where you can get any pizza, any size, for something like $12 (eat in). My wife and I joined a members' club there that gives assorted specials, and sometimes we get a $10 coupon that can be used against the special-prized pizza. It's pretty good having a pizza that's enough to feed us both and have enough to take home for another meal, for $2.
At first when the waiters there realised we were ordering a $12 pizza with a $10 coupon you could almost see their expectation of a tip disappearing. The first time we used it I think the pizza was $10.99 and the server looked as if he truly expected to be getting a percentage of 99c (he still looked after us, but didn't look like he expected much of a tip). But we usually have a couple of drinks with the pizza, and I still tip based on the menu price rather than the coupon-adjusted price. They don't do any less work looking after us just because we had a coupon. It's kinda funny when you get a coupon that's a huge proportion of the total cost, and the tip ends up being more than the final bill.
