A billion eh?

Well, some would go into a good money-saving account, probably some stable stocks as well.

Some would be donated to charities (for everything from disabilities, to people in 3rd world countries, for animals, for research to solve diseases).
Specifically: probably Spina Bifida research, research for the mental health field, cancer research, AIDS/HIV, poverty, animal rights/protection, education for those who can't afford it, money for orphans, money for poor families, and anything to help those in 3rd world countries.

Some of it would be given to my family so that way my sisters (especially) would have their education paid for.

I'd put money aside for the rest of my education, find a nice (small) place near my university - buy a dog, get my drivers license and get myself a nice vehicle as well (something economical preferably).

Then I'd save money so I could go on trips with my family during the summer and during the winter months.

Oh and I'd help my friends with their education if they needed it, make a donation to my university, and to the chaplaincy on campus.

And I'd totally throw a (small) party for people.