Rhino Laces
Rhino Laces are gunmetal-tipped boot laces purported to be totally indestructible. The makers claim that they "cannot be burned, cut, sawed, chopped, destroyed, or broken, or we will replace them for free." I haven't tested them myself, but I've seen reviews saying that they're even tougher than paracord, which is pretty impressive. If that's true, these laces would be perfect for outdoors…