Sweat wicking, quick drying, machine washable, one size fits all.
I never knew I needed a headband until I tried Dan John's Half-Hour Deadlift Challenge. (Pull 2 reps of 315 pounds every minute on the minute for half an hour.) At the 20-minute mark, my bar was slick with sweat. I tried a regular bandana but it kept slipping. And it looked stupid.
So I picked up a JUNK headband at the CrossFit Games and it did the trick. It fits flat, never slips, never drips, and makes you look like a ninja, not a hippie. Available in dozens of styles and colors. – Chris Shugart