I've had terrible service before. And not the "everyone is having a bad day" bad service, where you understand a bit. People have bad days, kitchens make mistakes, things get lost, but you can tell when people care. Those folks are often ones that wind up with a larger tip for fixing the problem or doing whatever they can to make it right....or not so good service.
I'm talking just the "I don't care" type of service, food is late, cold, wrong order, whatever. You are a ticket and they don't give a rats ass. I've intentionally left a $0.01 tip. If I left zero, then they might assume I'm a cheap A-hole. But $0.01 tells them I took the time to fill out the tip line, or place a penny on the table, and that they didn't deserve a tip. This is reserved for places that are top to bottom horrible experiences and I won't be returning anyway. The few times (I can count them on one hand) I've done this the place has been closed or sold within months.