Do you pronounce it "Roof" or "Ruf?" "Water" or "Wuhter?" Are little river shellfish called "crawfish" or "crayfish" or "crawdads?" Depends on where you grew up.
I loved this new dialect quiz at the New York Times, and thought you all might dig it too. It managed to place me pretty accurately—it had me in southern Minnesota/Illinois, while I grew up in Indiana with family from Minnesota. But more than the way it identified me, I really enjoyed the questions and possible answers. So many of them were idioms I hadn't even thought about, and several of them had changed for me as I moved from southern Indiana to south Florida to San Francisco.
The quiz is based on the Harvard Dialect Survey, and it's taken into account more varied idioms and pronunciations than I knew existed. Go take it, and comment below with how accurate you thought it was for you. (And sorry non-Americans, this one's really just for regional dialects. Though I'd be interested in what it finds for you, too!)