Clinical psychologist. I'm not sure if that counts, given that I'm in school to be one. In terms of challenge, variability, fulfillment potential--I can think of nothing else as perfect as this. My worry, though, is that I am not patient enough, or that I will become emotionally over-involved. I'm sure those will come with experience (hopefully).
Pie-in-the-sky dream job: being paid to frolick around different countries, learn new languages, meet all sorts of people, and write about my experiences.
Or, like, a rockstar.