In an article entitled WMD: A Primer by Eric Margolis three types of unconventional arms are called WMD: nuclear, chemical and biological.
Of those, the only true weapons of mass destruction are nuclear. The U.S., Russia, China, France, Britain, Israel, India, Pakistan and North Korea, alone possess them. Japan could make nuclear weapons within 90 days.
Without specialized medium and long-range delivery systems (aircraft or missiles), nuclear weapons are useless, even suicidal.