I think it would be interesting to see a Flying/Fighting type, although it may or may not be the best combination for battling. For one, although it would lose its weakness to Flying, Steel, and Rock, and have an immunity to Ghost-type moves, it would gain weaknesses to Electric, Psychic and Poison.
Design-wise, though, it would be interesting to see what a Flying/Fighting Pokemon would look like.
Oh, and FOR ONCE, I would love to see a free-standing, pure Flying-type. >_> I don't understand why they won't let Flying-types have their fun with their resistance to Fighting-type moves and pair them with Normal/Bug/Ice-types. That's just cruel. ;;