Bandanas are one of my must haves on backpacking trips let me go over some of the uses:

- Facemask: Look like a thug but maybe keep dust, cold, sun away

- Bandage: Good material for a night tight bandage in a pinch

- Trail Marker: Colorful bandanas can be tied around trees to mark a path

- Cloth Napkins: wash it in a stream and you are set

- Tissue: intended use

- Pillow-ish: A few times I have tied it around my head to my backpacking frame to prop up my head so I could sleep-hike on long days or early mornings.

- Use it as a thin layer to protect your hands when cutting small objects or veggies

- Scarf

- Hair tie

- Ice Pack: Just add ice

- Cool wet cloth: Just add water

- Lamp/Flash light shade: Tie it over your light source to get softer reading light etc

- Hobo-basket: Tie all corners together to make a pouch

- Different colors can help identify different people / teams

- Water filter: Sift out large particles

- Sling: Not comfortable

- Sleep mask

- Picnic cloth

- Dog Accessory