blue ring octopus - Produce a strong Nero Toxin called Tetrodotoxin. this Octopus uses as a defensively. It also has a Toxin that is Harleysville to humans and is used on its prey. This little fellow is found in Tide poles in semi warm climates.
Blue Ringed Octopi are no larger than a human hand and only display their rings when threatened. Their bite is highly toxic to humans; it's estimated that one bit has enough venom to kill 26 people, and there is no known antidote.