I have contractor bags in my BOB bag. They are nice and heavy that can be used as a poncho or help shelter you from a storm. Here is a list of 30 uses of plastic bags. Some I had never considered. But like most stuff, when living in a materialistic world we never really look at all the ways to use an item until we have to improvise. 30 Important Ways a Plastic Bag Can Save Your Life Not sure if the plastic bag is the most valuable survival tool but after reading this list, it has moved into my top 5.