Magnesium Phosphide: This solid can be converted into powder or granules. The phosphine gas it produces when introduced to acid or moisture is very toxic.
Methyl Bromide: Methyl bromide, commonly used in farming, can be a fumigant as well as a solid. It is so powerful than it has been banned in some areas.
Sulfuryl Fluoride: This pressurized liquid gas is strong enough to be used in lumber and auto manufacturing/cleaning. So powerful it can causes burns.
Chloropicrin: This liquid evaporates when released into air and was so powerful it was used in World War I as a chemical warfare agent. It’s not even used for food pesticides anymore because of its destructiveness.
Phosphine: This odorless gas works longer than other fumigants, though it can complete the job. It may very well be the weakest mentioned here though, as some bugs have developed resistance to it.
Methyl isocyanate: Made from rubber production, it is so powerful it must be carefully stored. Very toxic to all life forms.
1,3-Dichloropropene: Mainly used in farming, highly toxic and no longer used as frequently in Europe.
Hydrogen cyanide: Inorganic compound that actually boils at room temperature. Smells a bit like almonds, but deadly to rats and people.
Iodoform: A hospital like smell, and similar to chloroform and disinfectants. Less powerful, since it is actually used in some healing treatments.
Formaldehyde: Powerful enough to be a disinfectant and a preserver of bodies. Highly toxic to all living things.