Yugoslavia can't really be added to it since it has threatened no one except its own people. North Korea blatantly uses its sophisticated weapons program not to terroriise but to earn revenue. That leaves Iraq. We are, moreover, in real danger of misunderstanding the nature of weapons of mass destruction. It's one thing to make them under laboratory conditions, another to make them fly and seriously affect a sizeable target.
Biological weapons demand enormous technical prowess to use.
For truly deadly results they need to be dispersed in very low altitude aerosol clouds, which is extremely difficult to do. Chemical weapons to be effective need to be used in enormous quantities and, historically, most of those incapacitated by such weapons have not actually died. The worst case scenario, of course, is Iraq developing nuclear weapons. Yet even here we fall into the trap of exaggerating the progress made. Even India and Pakistan with all their sophistication have only produced bombs with yields that are Hiroshima size or smaller.