I can be cliche and say I'll probably help out needy families, homeless shelters, and a host of other charities; but, although I would do that, the first thing I would do is pay off my school Loans dude. Seriously! Those things are killing me! But after that I would do the usual; travel, travel to space, travel to mars, chill, make movies, and end up broke again; hopefully having achieved my dreams. If not, hopefully I had fun and screamed YOLO every few minutes.
After making sure my family and friends were all set for some time, I'd have a nice house by a lake and a big ol' garage filled with all my dream cars and boats. I'd spend my days our fishing, traveling, and just enjoying life. I'd also set a very good chunk of money away for my future children to go to college and not have any struggles in life.
Firstly I would make sure I was comfortable and safe, maybe buy a few houses or flats, live in one, rent out the other two at a reasonable price, I know its a billion! Then I would make sure all my family and friends are comfortable and safe for the rest of their lives, if there is still money left I would like to put it to work on helping the less fortunate, I hate to think that a lot of people are suffering because they don't have enough to eat and no safe place to sleep.