When my dad and uncle were kids, my grandfather encouraged them to collect walnut husks and put them on the floor of the garage to be driven over (very similar the tractor-technique described below).
While on the topic, someone has to speak up for butternut, also called the white walnut. As a related species, the nut of a butternut is very similar to a black walnut in several ways. However, the principle difference (according to three Foulkrod generations) is the butternut's refined and subtle flavor - lacking the bitter walnut taste.