Thanks again for the encouragement, folks.
I made up a bunch of messed up creatures for my AW game, and this is the horse entry:
Mustangs - the horses of the 101 superficially resemble their pre-Apocalypse ancestors, but are more like goats than horses. Two-lobed eyes of gold or blue peer out from matted white manes, and their gnarled red horns curve up and back from massive bull-like brows. Their short muzzles are filled with a frightening array of teeth, and their beards disguise a massively muscled set of jaws: they can eat almost anything, and in the wild, occupy an alpha scavenger role, occasionally hunting down other animals - even humans - when food is scarce.
Also:
Quilldeer - this quadripedal bird is about 4 feet high at the shoulder, with long, spindly legs, and its body is covered in sharp, spiny feathers. Its snaky neck ends in a birdlike head, with a long, swordlike beak.