I'll start.
For me, it was the 100 Days of No-Code Bootcamp that turned me from a lurker (since 2016) to a maker (since april 2022) and now I'm working full time in No-Code.
Which course transformed your life?
For me it was a creative writing course I took in college. I'm a math guy, so this was a big change of pace. Very difficult, but super rewarding to self-observe progress throughout the semester.