I should clarify that I've only left a 1-cent tip twice in my life and both of those times were extreme circumstances. In both cases the waitstaff were obviously lounging around taking advantage of the fact that the restaurants were nearly empty. In the first case, we called the manager over and even HE couldn't get the waitress' attention. In the second, the manager was goofing off just as much as the waitstaff so we didn't want to "bother" him with a complaint.

I know it doesn't happen often, but random violence is a fact of life. (I'm reminded of a story about 3 McDonald's workers who beat up a customer who complained about a runny milkshake.) If I can avoid confronting someone, I generally prefer to do so. If that means leaving a penny tip and walking out, so be it.