I didn't like the PDW fenders and those are the only reasonably priced fender options I could find for a fat bike, so I made some fenders for my Pugs out of 3/32" polycarbonate, check it out:

Sweet Fenders Bro.

They seem to be pretty sturdy. About an eighth of an inch of wobble in the rear, but not enough to cause any rub. Not meant for stomping as I'm sure they'll clog with mud and whatnot, but I can't stand being covered in wet slush. I use my fat bike for my transportation in the winter.