History of Biological warfare

During the past century, more than 500 million people died of infectious diseases. Several tens of thousands of these deaths were due to the deliberate release of pathogens or toxins, mostly by the Japanese during their attacks on China during the Second World War. Two international treaties outlawed biological weapons in 1925 and 1972, but they have largely failed to stop countries from conducting offensive weapons research and large-scale production of biological weapons. And as our knowledge of the biology of disease-causing agents—viruses, bacteria and toxins—increases, it is legitimate to fear that modified pathogens could constitute devastating agents for biological warfare. 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1326439/

Aren't all bioweapons scary? Definitely. But these 10 are particularly troublesome once they're released from labs and unleashed on an unsuspecting public.

http://www.stufftoblowyourmind.com/blog/list/10-scariest-bioweapons/

http://www.fas.org/biosecurity/resource/bioweapons.htm

http://news.discovery.com/tech/biotechnology/five-scariest-bioweapons-120514.htm

http://biology.about.com/od/biotechnologycloning/a/biological-weapons.htm