For applying Hoof oil / Hoof flex on your horses hooves, you'll find a small sponge works just as well as an oil brush.
Looking for some Horse Stall Toys? Clean out a milk bottle well and fill with molasses for your favorite equine. Poke a few small holes in it and tie it to a tree or rafter and watch your horse spend hours licking the jug to get the molasses out.
Horse Brushes that do double duty? Nail a few old horse brushes (the bristly ones) to the sides of the stall so your horses can rub against them to get at those annoying itches.