Fifty years ago today, the Willie D as the Porter was nicknamed, accidentally fired a live torpedo at the battleship Iowa during a practice exercise. As if this wern't bad enough, the Iowa was carrying President Franklin D. Roosevelt at the time, along with Secretary of State, Cordell Hull and all of the country's WWII (World War II) military brass. They were headed for the Big Three Conference in Tehran, where Roosevelt was to meet Stalin and Churchill. Had the Porter's torpedo struck the Iowa at the aiming pointy, the last 50 years of world history might have been quite different.
Via Jerry Pournelle [1], “Don't shoot, we're Republicans! [2]”
Nothing much to add here, other than it's an amusing story and I'm finding it fun to think about what would have happened had the torpedo actually struck the Iowa. I don't think much would have happened in the long run—FDR (Franklin D. Roosevelt) would have most likely survived, been transported to another ship and still made Tehran, but still, there was that slight chance he would have been killed.
Even so, I don't think the outcome of the war would have been that much different; Truman still had to take over from FDR before the war was over.
[1] http://www.jerrypournelle.com/mail/mail244.html