Coca-cola. It's black gold.
Porn - not sure that would really last beyond the novelty of seeing loads of artificially enhanced bums and boobs walking around. It would probably see me hooked on drugs and unable to get excited by my wife, as well as intellectually empty and morally void. Maybe.
I'd let everyone use windows for free.
People pay for windows?!
A small firm building their own supercars much like Noble but on a much smaller scale and using their own engines
The order waiting queue would be as long as the distance that Theophany's laugh sound waves can travel