Given the choice, I would choose to be a Fire-type Gymleader.
Most of the Pokémon I seem to train through the games tend to be Fire-types and I have do have quite an extensive knowledge of them. Perhaps if Pokémon were real, I would pursue a PhD, but that's a different discussion entirely, isn't it?
That would be one of my ideal careers in the world of Pocket Monsters. Just think, to be a Gymleader one would be a local celebrity and highly respected. Now, I'm not one for fame, but it suppose it could be quite welcoming if I were to live in a small town or on an island. I do believe I would quite enjoy training my fiery Pokémon day-in and out, not to mention mentoring the trainers that tend to congregate in the Gym.
Heck, with a trusty Arcanine, Houndoom, or Rapidash by my side, who wouldn't be content?
(You all though I was going to say Heatran, didn't you? For shame...)