I think that teaching classes would be interesting. I have a lot of industry experience, but I never actually got a degree in the field I work in, and I don’t have any sort of degree that deals with teaching. Is it possible to get a job as a teacher without those?
Edit: I’m in the US specifically looking at teaching college courses, but K-12 could be interesting, too.
Many states have accelerated certification programs for K-12 education, and while some subjects would require a specific degree for secondary grades, many wouldn’t. Then there’s guest lecturing, adjunct work, and sketchy for-profit places will bring on anybody who knows more than the students.
So, I guess it depends on who you want to teach, how often, and in what context.