The worst bike wreck I ever had, in pre-helmet days of the late '60s, happened not when I was trying something stupid, but when I was just going down a very moderate hill near where I lived, and a bee landed on my face. Of course, when a bee lands on your face, you swat it, but when you swat a bee while riding a bike, a bad result is likely. Although I remember trying to grab the handlebars as they quickly shook right and left, I was unsuccessful, and experienced a delightful meeting with the pavement. Fortunately, no bones were broken, and no stitches, but I probably still have scars from it :)