it has always been a dream of mine to talk to a customer that way but i never quite got to that level of fuck you. the best i ever did was tell someone, "go somewhere else, then", and i was 19 when i said it and had already given my notice. also when i worked at the supermarket at closing time i would get on the intercom and ask why everyone was still there, suggest they leave, etc. but i was only about 17 for that stuff and all the managers were long gone when i would do it. never on sundays, though. that was time and a half.
never got fired for it, though.