Personally, I'd love a Dullahan. Fairy/Steel or Fairy/Ghost. With the head replaced with a shield with a face so as to not scare the kids. The horse could be a separate pokemon. Maybe you'd get the headless knight in one version, and the horse in the other. If they are together on the field, they gain a stat boost.
A Leprechaun. It'll be the other pokemon line that can naturally learn Pay Day. Probably with Super Luck as an ability.
A Troll with Regenerator. Maybe Fairy/Fighting or Fairy/Dark.