I keep reading about incidents where tensions or mechanical mishaps almost lead to nuclear hostilities between the USSR and the USA, and would like to ask for as comprehensive of a list as possible detailing instances where the two nations came close to annihilation.
Arguably, the closest the Soviet Union and the USA came to a nuclear exchange was during the Caribbean (Cuban) Missile Crisis of 1962. The Soviets felt as though they were behind in nuclear capability because of the distance their ICBM's had to travel in order to reach the continental USA. As a result, Krushchev placed nuclear missiles in Cuba some 480 miles away from the American state of Florida. The justification of doing so was in order to protect Cuba from US interference as they had tried to topple Socialist Castro, at the Bay of Pigs a year prior.
As for other events that could have potentially led to nuclear exchange:
The 1960 U2 incident, where a US spy plane was shot down over the Soviet Union amongst others.
Reagan's Strategic Defense Initiative (also known as the Star Wars,) increased superpower tension drastically as the Soviet Union felt as though that the USA could protect itself from any sort of nuclear attack ridding them of their second strike capability. As a result, Brezhnev the Soviet leader at the time felt vulnerable to US attack.
Bear in mind that both nations were well aware of one anothers' second strike capability. Essentially, both the Soviet Union and the USA had accepted MAD (mutually assured destruction) as the only consequence if nuclear war were to ensue. While foreign policy makers such as Mcnamara argued otherwise, MAD seemed to dominate any nuclear discourse during the Cold War and as a result, the nuclear capabilities of both superpowers acted more of as a deterrent rather than pose a real threat.