The Impossible Quiz
Funny, loud, and almost a quiz. The impossible quiz requires you to think laterally and often to simply guess. Some of the levels are about speed while others are more about thinking. I've managed to get to level 60 or so, let me know if you do better!
I think this takes a looong time to load, so if you've got a slow connection maybe try a different game. Many thanks to Paul for telling me about this one.