I think other than throwing gas, (Molotov cocktail), and starting a fire, flare guns are over rated as weapons.
a slingshot, with some real shot has range and can hurt or kill. up to about 25yds. if you practice.
spear gun at < 20 yards, or cross bow, but nobody;s really going to carry one.
and nobody's going to blink if you have 5 spare spears.
and slingshot is for those damn birds, honest officer.