In season three of the Walking Dead we saw the survivors entering the prison and clearing out some of the walkers inside, both prisoners and guards. But when the guards died or were bit, some of them were still wearing their riot gear. Although they are just regular old, run-of-the-mill zombies, with riot gear they become pretty hard to get at. One of the great effects moments in the show was when Rick tore off one of their gas masks and its rotted face came with it. The super gross appearance of that wet face and it’s bulging eyes was a real freak-out moment for the episode.