Physical danger, like walking across a busy road without due consideration to traffic, or using knives. The two I know will sit for hours doing the same thing. What we call "commonsense" is lost on them. Bear in mind, as I'm sure you know, they are all different in the challenges they face. Being bullied in school is another because they can send out the wrong social cues and don't respond in the way their non-autistic peers expect. The two I know, one is in his twenties and the other about ten, don't have a realistic prospect of being fully independent, I don't think.