If I had unlimited amount of money, I would buy all the advertisement channels of the world and fill them with classical music. I would by all the billboards spaces and burn them to ground or if that is not possible, I will paint them sky blue with white fluffy clouds or camouflage them.
Just kidding (not really).
A bit more realistically, I would build an open source car company. I mean, a car which is 100% documented and documentation publicly available. with all the diagnostic tools and information how to use them available publicly.