Dead Hand

Here's a scary one. The Soviets set up a system to automatically launch a nuclear 2nd strike if their leadership were removed by a first strike. I came across Dead Hand (formally called the Perimeter system) in some speculation about the termination of broadcast by UVB-76. This lead me to the Wikipedia article on the Dead Hand. The whole thing seems like a bad Russian imitation of Skynet. Apparently, it may not have been totally automatic - there was a sort of Mechanical Turk in a deep underground bunker that could send a low frequency radio signal to initiate the responsive launch. Last year, Wired said that the system was still in place.