>(although what you'd then use that for is beyond me at this minute).
A bandana is the single most useful item in an ultralight backpacker's inventory. Aside from wearing it under a baseball cap for sun protection, you can use it to filter water into a bottle before treating it with Aqua Mira, as a towel (say you spill water in a tent), as oven mitts for holding a hot pot, use as a face mask in dusty weather, blindfold for sleeping, and to be more visible to hunters.
In an emergency, you can use a knife to shave off lint from it and use that as tinder for your fire, you can use it to soak up water from sources that you couldn't otherwise drink from like dew accumulated on plants, you can wrap wounds in it, use it as toilet paper, tear it into strips for cordage, collect berries in it, use it as a sling, for signaling, and a million other things.