A billion is a LOT of money.
I'd obviously pay off my debts, which is mostly just my house at this point.
Manage my way out of work over a period of 1-3 months.
Ensure close friends and family were debt free, including their houses and cars.
That's all barely touching the sides on this much though.
Put in place a range of very conservative investments, to ensure a safety net in all foreseeable circumstances.
Buy some local sports teams, or similar, which would effectively become my 'job'. I might do this in women's sport rather than men's, as the cost would be lower, and the money more impactful I suspect.
Call myself an author, and work slowly (but steadily) towards finishing a book or two. Which I could then get published, despite it's general crapness.
Buy a couple of nice cars. Nothing crazy, but I like nice cars.
Travel. There are a whole bunch of things I'd love to see and experience.
That's all the basic stuff I'd do.
Determine some charitable organisations I could make a real impact with.
In particular, I'd invest money into Neurofibromatosis research (my nephew is 11, and suffers from NF2).
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Neurofibromatosis - Better Health Channel)
I'd also make some money available to Patty Mills. He can either use it to run for PM (mostly joking...lol) or in supporting local indigenous communities. I honestly wouldn't know where to start with such things, but can see the value and importance in it.
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I have a man-crush on Patty Mills... | Religious Forums)
I suspect even after all of that, I'd have a truckload of money left over. But the NF research might just plow through a lot.
If not, I'd like to set up some academic scholarships to support kids who've managed to achieve despite tough backgrounds, etc. Social mobility is a key to a healthy society.
That's about all off the top of my head.
But perhaps effective. My list of such individuals might be an open secret. 
