[x] for all but offensive service

If you're in America, and you sit down to eat, or you have food delivered to you, you should tip. These jobs generally pay minimum wage or less, and the workers who take these jobs are relying on tips as part of their wage.

UNLESS: The server/delivery person has been grossly negligent in their roll of customer servant. Bad/cold/late food is probably not their fault, and punishing them by docking their wages for something they can't control is being petty.

IN WHICH CASE: If you decide to NOT tip, you should have a good reason, that the manager should want (and need) to hear in order to ensure positive customer experiences in the future. I mean, if you're offended enough to avoid adding a measly ~$5 to your bill, then the offense must be noteworthy, right?

If the service is REALLY terrible, you can tip $0.01 just to make your point to the server.