Really depends on your preferences. If you really don't care about money, biological research is always interesting (if you find a useful subspecialty to get into). If you're more interested in working with people, try healthcare. Nurses and mid-level practitioners tend to interact with people more often than physicians because of their changing roles (at least in the US), but if you have the time (and really don't care about money), MD might be your route.
>inb4 doctor money
I'm talking about debt/ROI for primary care, not salaries for surgeons, etc.
Engineering is great for working with your hands and not worrying as much about the politics of the job. Usually intelligence/aptitude determines your place in the field.
