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.
I’m sure it varies from country to country, but here in Canada, at least Ontario, which is the only province that I am familiar with when it comes to teaching requirements, you would definitely need to attend teacher’s college, which is a two year program.