No one really ever thinks about this but everyone should have a whistle while skiing. It is super easy to loose control and accidentally ski into oblivion. If you get in a sticky situation that you can’t get out of and need help, a whistle will come in handy for getting the attention of fellow skiers.
This seems like a no brainer but you would be surprised! I am one who always forgets my glasses! The snow can be blinding on a sunny day and when you are skiing the ice can fly up in your eyes. I find it impossible to ski without my sunglasses.