The most dangerous 256 error I have found so far occurred in the Therac-25 medical radiation machine. This was designed to treat cancer patients with bursts of either an electron beam or intense X-rays. It was able to achieve both types of radiation from the one machine by either producing a low-current electron beam, which the patient was directly exposed to, or a high-current electron beam, which was aimed at a metal plate to produce X-rays.
