My friend jogs in New Orleans. He liked the "PAIN" spiked knuckles by HeviDi, but doesn't want to hurt anyone THAT much. So, I took off the spikes and flattened the bottom a little for easier detachment from the rafting.
I printed them on a Makerbot Replicator 2 in PLA @ 0.20mm, 10% infill, 2 shells with rafting and no supports.
(edge231): "As a public service announcement for anyone who wants to make these: check with your state and local laws before you make this and start carrying it around. Some states do outlaw all types of knuckles like these, even plastic ones."