1. The power to give myself whatever power(s) I wanted, whenever I wanted.
2. The ability to learn foreign languages instantly, or really freaking fast.
3. Never have to use the bathroom.
4. Never have to eat, sleep, or breathe in order to live.
Power number 1 is the big one. I would never have immortality, unless I had a foolproof kill myself button. I think after the universe and all time and space ends, I might get bored.
Other than that, I would obtain significant training (probably through the Navy SEALs or USMC Force Recon), and after my years of service ended, I would sell my services to the US Military for lots of money. Either that or I'd take over the world, starting with Africa. Why Africa? Because it's already halfway done.