I would buy gold bars, one billion dollars in gold bars. Gold will always have value, and it wouldn't be difficult to spend the entire billion dollars in that amount of time. Afterwards I could sell the gold taking all the time I need.
I think it's interesting that everyone agrees that gold has intrinsic value. Why though? I mean think about it. Yes, it's fairly scarce, but what do you do with it besides use it as currency? Jewelry only uses gold because of it's status as a valuable material (and because it doesn't corrode). I realize there are myriad technological applications but those only use minute quantities of gold. So when it comes down to it, it seems that gold has value mostly because we all agree that it does, just as in the case of paper money. If society collapsed the only things with real value would be those that are edible, useful as building materials, useful in acquiring food, or useful in defending oneself.
Make it like Brewsters Millions..You can't have anything of value afterwards..could you do it? (That includes charities..b/c they give you a tax deductible receipt)
I would buy nice houses and give them to the poor and not charge them anything. With the rest of the money I would buy me 2 houses, refurnish them and buy lots of trips to a lot of places and buying a ton of books, and HBO so I can know what is going to happen in GOT. If I have anything left, I would give it to Unicef and other charities so they can help a lot more of people than I could already had
Acres of land for my horses and dogs. Stables, An showjumping arena, dressage arena, and an indoor and outdoor ménage.
Train dogs to go into hospitals and hospices and keep the patients company.
An adapted house for people who suffer with severe mental disabilities.
Gold.
Put money in my will for my future family.
And give the rest to charities of my choice (if there is any left!) :)