I would take that money, buy a high end super sport bike, and drive across the continent, then onto a boat, then across the next continent, then across the next...
Ugh that's tricky... probably what I would do is save up the money for me and my bf to get married one day (still early) save up for a really nice house and fix it up for any landscaping or adding onto the house. Save up for cars for me (Suv/jeep) kinda cars and any car my bf wants lol and save for disney/universal and a lot of travel. If I still had money left over I would donate to Dana Farber cancer for my brother and dad cause they had cancer and to the children's hospital :)
Probably buy a pretty nice house. Nothing too crazy, maybe a avarage sized house with heated floors, a pool and a hot tub. Think I'd also get a nice classic car and update it mechanically. In general I think I'd probably just live above avarage but not exsessively.
Purchase bungie and free them for Activision. Destroy destiny and give them the the funding for a better game. Buy up all the taken in the gaming industry and put them on staff.
Nobody here is thinking big enough. Well, in the 5 posts I read. At 1b$ you can already do anything. At 20b$ you can do anything x20. So what would I do? Simple. Build the world's greatest super yacht that has all the amenities needed to survive the end of the world. Obviously more for partying though. Has a boat garage, a place to park cars, and a detachable floating house. I'm thinking dome shaped. I saw something like that on Facebook. Next I'd throw money at diabetes and get rid of it. Yup. I'll get rid of cancer too but I'll make sure I don't get assassinated by some pharm guys. Then I'd buy a ton of lakes, rivers, and any other place needed to get clean drinking water. I'd make sure the water is free. If I could afford to I'd buy any big water companies I could.
I'd make sure me and my loved ones were set. Then I'd invest some to make sure the money lasts because I use a lot of it to feed hungry people all around the world.