A spare power band is a small, cheap, lightweight survival item that could be easily fashioned into a working slingshot and tip the balance in ones favor in a survival situation.

I have had slingshots since I was a kid, and I carry one one in my backpack today, and many a puffball and dangling walnut have fallen prey. With all that practice, I can't come close to this level of skill.

http://www.youtube.com/watch?v=9ieWrWLjii0