Apple Pie
The saying is "American as apple pie" for a reason: this sweet treat is a national institution. Forget anybody who will try to tell you pecan or key lime is better, because they are lying. The simple combination of sugar, buttery pastry and tart sliced apples produces a dessert so extraordinary people have devoted their entire lives to perfecting it. For a particularly excellent example, try the apple pie with added green chilies at the Pie-O-Neer, in Pie Town, New Mexico. Phone ahead and Kathy Knapp, the self-proclaimed "Pie Lady of Pie Town", will save you a slice.