What is must-have gear for mountain biking? All types of biking, mountain biking in particular: what are some must have items/gear to keep with oneself on mountain biking trips? I'm think of items such as extra inner tube, bike pump, etc...What products or items do you use? Specifics would be helpful, thanks!
For long rides of 1-3 hours, I carry the following:


Tube + mini pump (CO^2 if you want, tire leavers for new or difficult tires)
Mini tool with allen keys, spoke key and a chain tool
Water
Snack


For longer trips, you'll want to consider panniers (carry bags) and a hydration pack so you'll be able to carry the load more effectively. In general, advice on backpacking trips should apply.