Poison sting is a sharp-pointed organ used by certain animals to inject poison or venom into the body of victim leading to death or harmed to victim. Poison sting is acting as a defensive organ for animals to survive.
Stonefish and Scorpionfish possess dorsal spines which contain fatal venom; Sting rays store poison in their sting. Pufferfish soap fish secrete poison in their skin. Jellyfish and anemones have stinging cells called nematocysts (a specialized cell in the tentacles containing a venomous coiled thread) containing poison which kill the prey on the spot.
Some fishes possessing poison sting are sting rays, sharks, chimaeras, catfish, scorpion fish, stonefish, puffer fish etc.