>> "I like the cotton bandana because it does double duty as my sun protection, dish rag/wash cloth/towel, is my largest bandage in case of emergency (yes, not too sterile, but if it needs a bandana to stop the bleeding germs are the least of my worries). You can pre-filter water through one if necessary also. I've also used the bandana in conjunction with a beanie as a balaclava (over the face)."
I'll second (or third) the standard cotton bandana for all the same reasons.
How big is your noggin? I've got a fat head, and I use a standard cotton bandana... It's the only cotton in my kit. $1 for your choice of colors/prints from Walmart. These are 22"x22" (probably 24"x24" when new), and if folded correctly, I can completely cover my head and ears, though pulling them down over the earlobes means it rides low on the eyes, and covering the ears at all means no sunglasses.
I've never got a sunburn on my head/scalp (or top of the ears if covered) when wearing a cotton bandana, so there's got to be SOME sun protection there.
Since each is of the smaller size, I usually pack two... Red one for kitchen, and one of a half dozen other colors for everything else (hat/dew rag, washcloth, bath towel, etc.), If I was carrying a larger one, I'd probably only pack one (30" square weighs more than twice as much).
On edit: Properly quoting previous post.