Well, depends on what a zillion is. But I could see buying a bunch of land, onto which I'd build a luxury fortress with my friends (probably emphasizing practical gizmos more than high trim). I'd set up an investment system that would provide continuous income. Then I'd buy a fleet of cars, trucks, motorcycles, boats, all terrain vehicles (including Argos), military vehicles, and such. Then I'd buy all the tools I need to build boats and cars and guns and such from kits or scratch, with plenty of freakish conversions of all of the above - like a vehicle that can cross an ocean and a continent. Oh yeah, and a plane or two, and a helicopter or two. If I couldn't develop the skill, I'd hire a friend of mine to be my personal pilot by appointment, cause I know he has the skill. Then I'd go back to school and get several undergraduate degrees. Then I'd take care of a few significant needs of friends (actually before I bathed myself in such intellectual and material luxury).
If I managed to get that far without marrying, ie if I could see through every woman who would be after me only for money, I'd raise a militia to go tip the scales in a few African wars, like Sudan. Yeah, try to feed them too, but with peace and a fair government their own agriculture would be far more successful.
I'm guessing a zillion dollars actually doesn't mean unlimited funds. So I guess I'd have to prioritize between all of the above, and more.
Trust is earned, not... GIVEN away. - Worf