I'm an American
And I tip generously, so long as service is on par or better. Par meaning I don't have to keep reminding you for drink refills, my meal is cooked as requested, and any options (condiments aside from mustard and ketchup, any special cooked sides etc) are present and accounted for. If I am at a table with multiple checks, I take into account how you've treated others at my table.

I still tip for off par, but it is in ridiculous denominations, or hideous percentages (0.5%, paid in pennies, with an odd button thrown in for example). The only times I have ever been opposed to tipping anything at all were in situations where I was in a large group and "gratuity" was included in the check (how is it a gratuity then?). You can refuse to pay those anyway, by law all you have to pay is the check balance, but in order to make the establishment believe that requires a lengthy discussion, and both times I was on a schedule that had no flex in it.
(blinkin the merrily misanthropic IT gremlin, Tue 23 Jun 2009, 20:50, Reply)