Several months ago a Qantas Link flight attendant on a B717 from Melbourne to Launceston was attacked by a deranged passenger hell bent on rushing the flight deck. The flight attendant in question, who was the Cabin Supervisor, placed himself between the attacker and the flight deck door.
The passenger was weilding wooden stakes, which he proceded to use as weapons, stabbing the Cabin Supervisor in the back of his head repeatedly. The C.S. managed to tackle the passenger, wrestling him into the cabin and eventually onto the ground, where he continued to be stabbed until surrounding passengers managed to subdue his attacker.
Although this story lacks an 'accident', it certainly avoided one, god only knows what may have eventuated had he gained access to the flight deck.