I'd buy a faster internet connection, a mansion on a hundred acres of land, make a paintball arena, post-apocalypse themed, start a movie studio to make my movies, buy all the current and last-gen consoles, a home theatre (proper theatre), a few Aston Martins, a jet, a helicopter, donate a crapton to the Humble Bundle (say, $5 million), buy myself an ultrapowerful computer, umm, running out of ideas now...
Oh, right, and pay off all my debts.
So, I got bored, and calculated what this would all come to. Sort of. I guessed a lot.
$34233000
I still have over $6 billon.
Alright, fund another Indy movie, a good one, fund a Doctor Who movie made by the BBC, fund the next Bond film, after Skyfall, buy Valve, if only to find out what's happening to HL2 Ep 3, or HL3.
EDIT: Changed my mind. Humble Bundle would get $50 million. And then I'd spend maybe $2 billion on other charities, for things like cancer research. Because, seriously, fuck cancer.