What Type is your favourite?
Probably Fire. Even though you can choose a fire type for a starter, after that there's a relatively small pool of pokemon to choose from. There's some legendary's, some early generation pokemon, and that's it. So, even though they're easy to target, their general appearance is always cool and they have some massively powerful moves.
Secondly, Ice. Again, they look awesome. They get paired up with some other odd types, they can nearly all learn water moves to counter fire, rock and steel and they are also a rare type.
Finally, in third, I would say Flying for it's sheer diversity. You can have a flying pokemon