A little headband. A lot of people recommended Halo but that was not available for me so I picked what looked like the next best thing on Amazon, Grip Grab or something, and it works wonders. It does get completely soaked as in, when I stop at the top of a climb I could wring it and lots of sweat drops out, but somehow even though it must surely be fully saturated, no sweat falls into my eyes any longer. And I tend to sweat quite a bit.