- a helmet! I think I would have died several times if I was not wearing a helmet.
- a small screwdriver. This could save you the cost of a new binding or just help you adjust them for the powder day.
- a lock. An easy way to prevent losing several hundred dollars.
- your own food. Ski resorts charge so much for food and get away with it because they have no competition on the hill. But you can get around that by sticking a food bar or a bag of nuts in your pocket. ;) Plus, when you bring your own food you can make sure it is nutritious.
For home: an iron, wax, and scraper. Waxing your board by yourself is quite easy, takes only about half an hour, and is like $30 cheaper than having a store do it. It is good to wax snowboards every 3 to 5 rides.