If you're stuck outdoors for an extended period of time during the fall or winter months you will need to make a fire at some point, which can be a big problem if you don't have the right gear.
In an ideal scenario you'd have a lighter, matches or fire starter with you when you get stuck in the wilds, but as long as you have a sandwich bag you can use the power of the sun to ignite kindling.
Oddly enough a battery and a foil gum wrapper can also be used to start a fire:
A one-handed way to make fire. Connecting the foil of a wrapper to the positive and negative ends of the battery creates a weak circuit. Since this foil isn't built for that transfer, the energy has nowhere to go. The end result is a flame.