Well, the Houses aren't marked by exclusivity in personality traits. By this I mean that G. isn't the house for "brave" people who aren't smart or ambitious or social. Everyone has some of those traits. But which trait is the most marked? A G. can be plenty smart--Hermione is the smartest student in the school, for cryin' out loud. Cedric was plenty brave but was in Hufflepuff. But, Hermione is even braver than she is smart (if that makes sense).

I think many of Slytherins are incredibly brave--think of how brave you must be to hang in Voldemort's inner circle: the guy can kill you any time he wants to and yet you want to be close to him. Why? Because your ambition drives you to obtain the possible power he is offering. So, while it takes a great deal of bravery to be in the presence of Voldemort only those who have overarching ambition do so. Snape is the bravest man in the books after all.

jpj