I always thought it would make sense if there was a Light type. It would serve as a foil to the Dark type, with both types being super effective against the other.
^ I second the light type. I always joked around about them making a Zombie type. I guess it would be kind of similar to ghost?
Deja-vu from really old thread, but I liked the way I explained the idea last time so I'll re-use it. Rift type. Immune to Psychic and Dark (those types which most closely attempt to communicate between Rifts in dimension) Neutrally damaged by Ghost, but super-effective against it. Rift types are however the only type weak to Normal ("normal" typing representing a prototype baseline of a foreign dimension), and is also resisted by Normal. All other type interactions are completely neutral. Rift types cannot be put to sleep. This type represents some inter-dimensionals which became known as Pokémon, there would be few though not all of "legendary" power. Color represented is pure white, similar to what Normal type things look to us now but such a lighter white it makes Normal appear as a middle-gray between Rift and Steel If I was tasked with making one that would be it, though for the record I don't actually think Pokémon needs any new types.