If you had a billion dollars, what would you buy?

Invest? Spend? Give it to charitable funds? I think the first thing I would is go downtown in a major city and dump a million of it (in $20's) off of a rooftop and watch people go mad for it. I would buy a sweet car, invest some, and give to charity as well. I guess I could pretty much do what ever I want. What would you do?