Hetalia x Harry Potter. Because countries are just as easily sorted as wizards, obviously!
EDIT: Germany in Slytherin is not to say that he is evil, just that he is extremely ambitious and has in the recent past, shall we say, "stepped on a few toes" to get his way.
Similarly, America in Gryffindor is not to paint him as eternally a shining force for good or something. The point is that he values heroic ideals above all, even if he sometimes makes very stupid mistakes.