Adventure Medical SOL Emergency Blanket - $4.45

You wouldn't be caught dead wearing Adventure Medical's SOL Emergency Blanket ... by which we mean this emergency shelter features a metalized fabric that reflects up to 90 percent of your body heat back to you. It could save your life if you start experiencing the symptoms of hypothermia. And while emergency blankets aren't a panacea against freezing cold, they can be tied up for an improvised shelter, to signal rescue teams, and, when used correctly, save the life of a hypothermia victim. Also, this blanket is insanely lightweight and affordable, so while it will never replace your -40 degree sleeping bag, there's really no excuse not to carry one in your pack. - $4.45