Princess Diana. It was SO sudden, and she was so young, and it was all for the lack of a seatbelt. I've always thought it was a short enough distance that she just didn't bother, although her sister said she was usually a stickler for seatbelts. But they are fiddly and annoying in the dark. I expect she thought it would be OK. Just a seatbelt click between life and death. So tragic. (Crash experts said she'd have survived if wearing a seatbelt, since her side of the car was not crumpled and her chest injury was because she hit the seat in front.) She used to be everywhere, in the papers the whole time, for years, and sometimes I still can't believe it happened.