I don't know if it's been mentioned before, but the one that really annoys me is Mythbusters. They always claim that they do everything with safety in mind, but when it comes to firearms handling they're complete morons. Things like the improper use of chamber flags by sticking them in the muzzle instead of the chamber, or Adam aimlessly waving a pistol around with no regard for safe direction, or even chambering a round through the ejection port on a semiauto. These not only don't teach someone the proper way to be safe, but they teach people that it's ok to be unsafe with firearms.