Robert Clay Allison (1840-1887) was a hell-raising cattle rancher and shootist with a violent temper. In 1862, he got a medical discharge from the Confederate Army for a mental disorder, possibly due to being struck in the head years earlier. In 1871, he stole 12 government mules; when he tried it a second time, he shot himself in the foot and had a permanent limp. He was known to ride through towns, shooting his pistol; once he supposedly rode nude, wearing only his pistol belt. He killed an estimated 15 men, but he died in a freak accident: he fell from his wagon and a wagon wheel ran over his neck, killing him instantly.
Clay Allison was a known gunfighter in the old west known for being the man who "Never killed a man that didn't need killing.".