Ooh, this is tricky! Ivan, for instance, I was going to say, is blatantly a Hufflepuff, but then, the instinctive rescue-kittens-from-trees-without-considering-the-consequences is pure Gryffindor.

I'm tempted to say that Miles Vorkosigan is a Gryffindor and Admiral Naismith a Slytherin... and where will that leave Mark?

Duv, surely, is pure Ravenclaw.