Is there a very stinky chemical solution that isn't a health hazard? An effective way to disperse rioters &amp; looters would be to send an armored vehicle in to spray them with a very stinky liquid. Is there a chemical that stinks but is not  a health risk and that breaks down after a few hours, or could be neutralized with another solution after a few hours?
My vote would be for butyric acid and related short-chain fatty acids with between 3 and ~8 carbons (isobutyric acid, valeric acid, isovaleric acid, caproic acid, etc.)

In pure form these chemicals would be dangerous acids, but in dilute aqueous solution buffered at pH 5 or so, they are not very corrosive or toxic but are still pretty stinky.

Skatole could be another example.  See the Wikipedia article for malodorants for some more ideas.