Is there ever an instance where the USA should use WMD, nuclear or otherwise?

I don't think there is ever a time when WMD should be deployed. Despite down scaling the level of wmd world wide we still have enough to destroy the world many times over. WMD are not good for so called targetted killing as it will kill many inocent civilians in its wake. Hiroshima and Nagasaki are both testamount to that and they were relatively small primitive wmd. Also, as soon as one country uses one, it is highly likely that weapons will be launched in response. And that really is end of the world stuff.