Entrepreneurship. It's a lot of upfront work, but you've got the ultimate upside in terms of money, control over one's lifestyle, impact, and fulfillment.

But more realistically, I'd probably pursue product management because it seems interesting and isn't hard to transition into as a developer.

If I didn't have to worry about money, then I'd be trying to make the world a better place, doing things like spreading awareness of and advocating for a basic income.