Probably the most impulsive thing I did was join the Army. I was a pacifist and everyone considered me nerdy and weak. I was trying to put myself through school, and failing at it. I had bicycled past a recruiting station and in a whim, thought, what the hell, nothing else is working, walked in and signed up. It was a crazy thing to do. In retrospect, it was the turning point of my young life. Even though there was risk and deprivation at times, if I could rewind my life and make that decision again, I would do it in a heartbeat. But doing it with no information and on a whim was pretty stupid.
I made some stupid moves when I had a motorcycle but somehow did not wind up as an organ donor.