This is an interesting thread idea, so what the heck, i'll start!
For me, it was dropping everything and moving down from Canada to date and eventually marry my now wife. It was scary, fraught with difficulties, but it was the best decision I ever made.
A little silly, but I’m proud of passing both of my CompTIA A+ exams on the first try. That was back in 2007, but that led me down my current career path and landed me a job that I really love.