I would either be a Dark or Psychic-type gym leader :P
Dark Pokemon: Umbreon, Bisharp, Spiritomb, Weavile, Honchkrow, Scrafty (setup and amount of pokemon on team varies with starters/amount of pokemon on-hand with challenger).
Psychic: Alakazam, Espeon, Bronzong, Mr. Mime, Xatu.
Badge: Shadow...