I usually carry a road flare when deer hunting. Not only can they be used for signalling, but they, as someone already stated, can be used to dry out and start just about anything.

They are very visible at night, the red glow can be seen over and through the trees pretty easily. I shot a deer at dust one time. By the time I started to gut it night had fallen. The small flashlight I had was inadequete so I popped the flare. Not only did it cast light, but my brothers saw the glow and came to help.

They also put out quite a bit of smoke, if nothing else, can be smelled a long way.

I don't know if I would carry one while backpacking because of the weight, but for hunting or being out in foul weather, they are pretty good insurance.