Thought we could have a little discussion about the things you absolutely must have when hitting the trails, and no whiskey is not a must have 
Dual End Wrenches
Always good to keep a couple multi-sized wrenches on board in case you're forced to make repairs out on the trails. No one plans to brake down, no matter how well you take care of your machine no tools= not fixing it. Probably pretty safe with carrying at least 10/12 mils and 14/17 mils.
Matches
Again no one plans to break down or get lost, BUT if the worst goes down do you really want to spend all night in the dark and damp cold? Simple precautionary measure can provide comfort when you need it most.
Cell Phone
As long as you have service it will be almost impossible to get yourself lost.
TP
We're not bears and no body ever looks forward to picking up a pinecone for purpose use. Chuck it in a ziploc, one day you will be thankful
Zip Ties
The side by siders duct tape. Stash a bunch in multiple sizes, considering their uses are almost without limit there is no excuse not to have a bunch just in case.
Tire Kit
Including the patch kit and a Co2 inflator. Its all well and good if you patch the flat but riding on a uninflated tire is going to chew up the tire 9 out of 10 times, not to mention hamper your performance. Nobody likes limping home.
Multi Tool
Doesn't really need explanation, carry a bunch in one. What would you rather a tool chest, or worse none?
Rope
How useful is 15 or 20 feet of rope? So useful that you won't know how badly you need it until you don't have it.
These are just some basics, feel free to chip in some of your other must haves.

Dual End Wrenches
Always good to keep a couple multi-sized wrenches on board in case you're forced to make repairs out on the trails. No one plans to brake down, no matter how well you take care of your machine no tools= not fixing it. Probably pretty safe with carrying at least 10/12 mils and 14/17 mils.
Matches
Again no one plans to break down or get lost, BUT if the worst goes down do you really want to spend all night in the dark and damp cold? Simple precautionary measure can provide comfort when you need it most.
Cell Phone
As long as you have service it will be almost impossible to get yourself lost.
TP
We're not bears and no body ever looks forward to picking up a pinecone for purpose use. Chuck it in a ziploc, one day you will be thankful
Zip Ties
The side by siders duct tape. Stash a bunch in multiple sizes, considering their uses are almost without limit there is no excuse not to have a bunch just in case.
Tire Kit
Including the patch kit and a Co2 inflator. Its all well and good if you patch the flat but riding on a uninflated tire is going to chew up the tire 9 out of 10 times, not to mention hamper your performance. Nobody likes limping home.
Multi Tool
Doesn't really need explanation, carry a bunch in one. What would you rather a tool chest, or worse none?
Rope
How useful is 15 or 20 feet of rope? So useful that you won't know how badly you need it until you don't have it.
These are just some basics, feel free to chip in some of your other must haves.