Although just a simple piece of cloth, a bandana is one of the most useful things you can carry. Haven't got one? They're cheap. Buy three, and buy the largest size you can find but make sure they're 100% cotton. Traditionally they are used as a large handkerchief, but a bandana's uses are only limited by your imagination.
On a hot day you can wet it and tie it about your neck and have a personal evaporative air conditioner. Forgot your hat? Roll one corner up, tied the adjacent corners together, then tuck the last corner under the knot and you've an instant do-rag. Running away from home - tie the corners together and hang it on a stick and you're ready for the road. Still not convinced? Here are just a few things you can do with one