Ghost/everything. We just plain don't have nearly enough Ghosts. Sure, they're supposed to be Pokemon that you can't hurt or find, but c'mon, Gengar's always been the most useful non-lgendary Ghost. It's hard to believe that, other than its Psychic weakness, that it's still the only option for an offensive Ghost type Pokemon. It has the best overall stats, excellent Speed to boot, and the best moveset, and I mean the best for its uses.