Sorta heavy and maybe not the intent of the thread, but easy, two days in particular. One helping load a person on a sled at an industry demo day. Looking at his face, I knew he had probably already passed. He'd had a high speed impact with a tree. It was awful. Oddly enough, I took a couple of runs immediately afterward to sort my head out. Didn't know what else to do.
The other, and the worst, at the top of Powder Bowl at Crystal. I had an all mountain youth group. New snow, beautiful day, kids are pumped, then the call came from home, mom in tears telling me to come home for dad. My immediate supervisor who was skiing with us took the group and I headed down the hill... I could barely ski. Got a plane home the following evening and got a few hours with my dad before he passed.
Skiing wise, sure, I've screwed up exams, had days when I couldn't have made a turn and chewed gum at the same time, but those days are small beers bad.