Not quite a nuke (just try obtaining enough uranium ore) but there are some fairly dangerous things a determined nutcase can make without drawing suspicion.

Example determined ned nutcases include Aum Shinrikyo, who tried anthrax, botox, and nukes before succeeding with sarin gas (thank IG Farben!) among other things.

It's a fascinating (if troubling) story: https://en.wikipedia.org/wiki/Tokyo_subway_sarin_attack#Back...