Stuck out in the wilderness about to freeze to death?  Get some ice.

No, really.

Ice LensMythbusters ran an episode (#45) about using ice to make a fire.  The gist of the design is to shape extremely pure ice into a large lens a few inches thick and about the size of a small dinner plate.  The ice is then used to focus light from the sun to slowly create a fire.  You’ll need some extra dry tinder finely separated.  One guy on the net has laid out full instructions.

This is one of the more unique survival tips that I found interesting enough to write about.  If you try this out, let me know how it goes.