I would definitely not buy a private 777, even though it is a tempting prospect. I like travelling on actual airlines.
For what I want to do, I would need a few more billions, but I would probably:
Donate 50-100 million to selected charities
Put 200-500 million into investment and holding accounts
Use the rest to help finance the actual construction and/or research and development of various civic projects in San Diego (a new airport, ballpark, redevelopment of residential and business/industrial areas).
A billion is a lot, but still not enough....