Oh, twice for me. Once when I was 10, I was driving a go-kart and the place I was at, the operators failed to inspect each of us (being in a small group) and apparently I had my seat belt on wrong (again, they failed to make sure), I hit a guard rail and the seat belt came 1/8th inch from hitting my juggler vein.
7 years later I was hit by a so-called best-friend who was messing with his radio while I was on my bike, however if that had not happened, I wouldn't be here today due to another issue that was caused by my mothers negligence of taking care of me properly when I was only a baby. An ear infection ate away and destroyed the left mastoid bone (the bone keeps the ear canal in line to allow hearing) and the result from that was skin growing in it's place and up inside of my skull pushing against my brain which in turn caused memory issues as well as learning difficulties.