Either an artist, novelist or film maker, a reclusive one at that who lives alone with several cats in a huge mansion. I'd have to be already rich so I can write/sculpt/film what I want to rather than my paymasters (bosses) telling me to only do something that will make maximum money and making me edit my preferred work. Being already rich will mean I'll be able to devote as much time and energy into my work as I need without having to worry about bills or time constraints etc.
Head of a medical research company with massive funds and little pressure on making profits, I'd try and find cures for diseases that kill so many people. I believe it's possible as military budgets are huge and look at some of the fancy weapons we have yet medical research companies have to beg for money or rely on donations which isn't really fair.
Run an aid organisation again with huge funds where I could look at grave situations worldwide where my organisation could really make a difference and save loads of needlessly lost lives, people who don't have a chance from the day they are born unlike those born in the west who bitch and moan about not having this or that etc