One dragon that I think would be cool is the I mentioned before: the land dragon. The only instance in fiction that I've seen that was in "Vision of Escaflowne". Very often we think of dragons that can fly or swim. But because dragons were inspired by creatures like crocodiles, alligators and snakes, it would stand to reason if there were such a dragon that couldn't fly but merely walked on two great legs, basically like a T-rex that breathes fire.