A mirror may be a vanity item for some, but it can also help you survive a worst case survival scenario. If you're able to find food, water and shelter then you're giving yourself a leg up survival-wise, but you still need to find rescue if you want to make it home. The trick to this is packing a signal mirror, something no survivalist would be caught dead without.
Any old small mirror will work for signaling, but companies actually make them specially suited for this purpose. These are typically made of something besides breakable glass, like Lexan. Some of them float or have nylon ties you can use to strap them to your backpack. Size isn't important here -- even a small 2 by 3 inch (5 by 7.6 centimeter) mirror flash can be seen from 100 miles (160 kilometers) away. Signal mirrors work best on clear days with direct sunlight, but you can also use them on overcast days. Not only that, but you can reflect headlights, flashlight beams and even bright moonlight for rescue.