12. Phosgene
Chemical weapon is proven to be as dangerous, if not more, than guns or bombs. And phosgene is arguably the most dangerous existing chemical weapon ever used in a combat. If you disagree, I have 120 deaths and over one thousand casualties to back that up.
Rest in peace, British troops. They had no idea what was coming their way when the German dropped 88 tons of Phosgene gas on them back in 1915. The gas may not be so toxic, but it attacks lung tissue in just a few minutes.
Not to inspire anyone to do it, but phosgene is actually pretty easy to make. In fact, it is used in fabrication of plastics and pesticides. Just expose chlorinated hydrocarbon compounds to high temperature, you get yourself this choking agent. I suggest you not to try this at home because without proper protection, you will be its first casualty.
Exposed yourself to phosgene gas, you will be coughing, choking, and vomiting to death. The worst part is that it is almost colorless and it smells like freshly cut grass.
