Eventually everyone does die of natural causes. It's just the wait that seems to be the problem. As for an accident, it's not so much an accident if you cause it.
With that said, I understand you're pointing out an ideal scenario. It'd be great to simply die in my sleep one night. Not so sure about the accident part though, I'm picturing car accident, which is seldom pretty. Medical accident, I could live with, as long as it wasn't painless.