These are just great. Know how to tie one correctly, and you can have a lot of fun. With this color, it'll match pretty well with BDUs and keeps your face covered up. It's a lot more convenient that panting your face with make up and have sweat ruin it all.
So, good for keeping dust, bugs, nuclear fallout, etc out of your nose and mouth, soaks up sweat to keep it from running down into your eyes (Which can be a real pain), let's you go on longer before getting sunburned, keeps your face from freezing due to chill, and good for camouflage. You can even tie it on over a sniper rifle or something. Just let yourself get creative and find a good use for it.
And at only $10? I think it's a great deal.