More Black Swans?

I have argued that the best way to think of “black swan” events is as developments that, even though low-probability, can in fact be contemplated ahead of time. Even if they are the sort of thing that has never happened before within an analyst’s memory, similar things may have happened before in the distant past or in other countries.

What current possible shocks have probabilities that, even if fairly low, are high enough to warrant thinking about now? Some have been discussed ad infinitum, others hardly at all.