I did it for FMA, and what I came up with was as follows:
Gryffindor: Edward Elric, who puts himself fearlessly on the line constantly for the sake of his mission of finding the Philosopher's Stone.
Ravenclaw: Shieska, who lives in a house full of books and literally reads anything she can get her hands on.
Slytherin: Roy Mustang, who is determined to become the Fuhrer of Amestris and is not above manipulation when he deems it necessary (i.e., the train incident).
Hufflepuff: Alphonse Elric, who shows compassion to everyone from Scar to a stray kitten left out in the rain.
So I'd like to toss the question out to the group: If you were the Sorting Hat, and you were presented with the cast of FMA to sort, where would you put them?