Well after investing in a way that a billion dollars a year would be interest, I'd fund a few dream projects:
Rob Zombie's Home Alone
Tim Burton's Plan 9 from Outer Space.
Chris Nolan's Green Arrow
Kevin Smith's Rear Window.
Guillermo Del Toro Invasion of the Body Snatcher's.
For no other reason than I want to see them.
Also, I'd invest in the Asylum so they can have 300,000 a movie for one year. Not too much because part of the charm of Asylum is how cheap they make movies.
After that, I would get into a deal with the Mouse to pay for a final half season of all their Marvel animation series since they bought Marvel.
Then I would go to Pepsi and pay them however much it would take for them to make a limited edition run of Crystal Pepsi.