Surgeon - To fix what's broken.
Gene therapist - To find ways to treat diseases.
Any kind of artist/musician - To deeply move people.
Architect - To create magnificent structures.
Explorer - To go where no man has ever gone before.
Inventor - To change the world with my inventions.
Oh, I'd also like to hand out business cards with "Profession: Genius". Being an all-around genius would just be so cool. I'd be able to dabble in anything I set my sights on and improve aspects of the world that really need improving.