When it's hot, sunny, buggy, etc., there's no substitute for a kaffiyeh. It's a hat, a scarf, air conditioning, a bug net, instant shade, a tourniquet, a filter, a rag, the list goes on. Cheap, easy to store, easy to wash, durable, and essentially disposable. When it's 105º+ in the desert, my wet kaffiyeh on my head makes it seem 20º cooler. Instant comfort.
Only downsides is that it's kind of a trendy piece of gear, and depending on where you stop in for supplies, it can attract some funny looks from the...ahem...locals.