Qualifications
Aside from temperament-oriented qualifications—the ability to thrive on Fear Factor or Survivor, coupled with little need to eat or sleep very much—you'll need a medical degree. It'll also help if you're able to speak foreign languages, especially French. Some other languages are particularly useful as well, such as Spanish, Arabic, Farsi, Russian, and Portuguese.
And to think, you told your mom you didn't need to study for your Russian final because it wouldn't ever come in handy. Shame on you.
Another thing that'll be very helpful is if you have emergency room experience. Lots of it. If you can get some experience in surgery, pediatrics, and internal medicine, too, it'll help as well. We don't have a crystal ball, but you might find these particular skillsets useful on your MSF missions.