I may have hit someone once, but it was so long ago I'm not sure if I remember.
A few years ago. I was resting near the lift line corral, a little away and to the side of the entrances, so as not to impede traffic, leaning on my ski poles, when a snowboarder slid by and chopped my poles out from under me. Hit didn't make bodily contact, but I went down after the poles went away.
Another time, a girl in our group, who was a pretty good skier, but a newby snowboarder on this particular day, ran over my new skis (first time out, even). Later, she ran over her dad's skis. Then, later on, she ran over another of her friend's skis. By the end of the day, she'd nailed every skier in our group, but had managed to avoid running over my son's snowboard.
The following year, that same dad had his feet chopped out from under him by a runaway snowboard.
About 1975, on New Year's Day at Winter Park, I observed two skiers having a head-on in the middle of Cranmer, a popular blue groomer. I was about 50 yards away and no one else was closer. Their trajectory was observable and predictable for quite some time before they hit, and it was a pretty hard collision. Neither skier made the slightest attempt to avoid the inevitable. I chalked it up to twin hangovers from the night before. I had skied New Years Day for several seasons before that, due to the light crowds compared to weekends, but I stopped doing it after watching that smashup.