Probably donate to a hell of a lot of FLOSS projects and push some of my favourite games as much as I could. If I had "Fuck you" amounts of money from it I'd likely just start funding healthcare and shit around the world (the noble option) but in a more "Random dude wins lottery and does better job funding healthcare than govt" fuck you kinda way.

I'd basically just try and do all my dreams if it was enough money to do it.