Neatorama has a cool article about near fatal nuclear incidents…

I like this one:

On October 25, 1962, again during the Cuban Missile Crisis, a security guard at an air base in Duluth, Minnesota, saw a shadowy figure scaling one of the fences enclosing the base. He shot at the intruder and activated an intruder alarm, automatically setting off intruder alarms at neighboring bases.

However, at the Volk Field air base in Wisconsin, the Klaxon loudspeaker had been wired incorrectly, and instead sounded an alarm ordering F-106A interceptors armed with nuclear missiles to take off. The pilots assumed that a full-scale nuclear conflict with the Soviet Union had begun, and the planes were about to take off when a car from the air traffic control tower raced down the tarmac and signaled the planes to stop. The intruder in Duluth had finally been identified: it was a bear.