I don't know much about dogs but I agree that Sam would have a very loyal dog. I thought about a German Shepherd but those can be quite fierece at times... although Sam too, so maybe it would be a good match. Does anyone know a race of dogs as loyal but a little less fierece?
I was thinking, what kind of animal would Gandalf have? perhaps an eagle, or a hawk... keen eyed, quick and strong. Or a monkey? good for lerarning things