If I had no further need for money (e.g. if I could provide for my family at a middle-class level permanently), I'd landscape full-time.
Science fiction writer and/or working in biotech.
My degree was in biochemistry... that's what I thought I'd be doing, but there was no demand for more entry-level biotech workers when I graduated and lots of demand for programmers. That being said, I think I enjoy programming more than biotech.
I would be coding for fun :-) Working in languages and toolchains of my choice (Clojure, f.ex.), helping organizations worth helping (NGOs,...). But that would be only a part-time activity, I would use the other part for stuff I like & never have enough time for - yoga, teaching, ... .
Maybe it is still the kid in me but professional racecar driver. I use to tear cars down and build them up when I was younger. I never have the financial/family support or knowhow to race full time.
Writing sci-fi, fantasy, and horror novels with a lot more focus.
Hmmm. Maybe I would try to gather some money for creating a music instrument shop/service. I like music and technology (behind music) as well - that would be fun!
I wanted to be a architect when I was younger.
Now that I am older, I am wanting to be a programmer. Architecture is like being a chef, but with more liability and fewer happy customers.
I always loved cooking, but the long hours, high stress, and low wages turned me off from becoming a chef.
I have always wanted to study combinatorics or linear algebra at a graduate level.
Novel/screenplay writer, or a journalist for technology or art related subjects.
Live in countryside, take care of sheep and planting!