My buddy Richie sent me the Meat Loaf pie graph with the explanation: "Funniest attachment I've seen in a long time. Not because I like the artist, but because I like pie graphs."
Personally, I've always been a fan of the bar graph. And not simply because I prefer bars to pies, but because I believe them to be a better visual representation of data collected for the purposes of showing contrasting values in similar entities.
Shaded maps are also pretty effective.