Pufferfish
While these interesting looking fish are well-known for using their inflation to scare away predators, their deadliest defense is their toxicity. Containing tetrodotoxin, which is 1,200 times more lethal than cyanide, the substance is able to kill 30 humans and as of yet, there is no antidote. Symptoms include a numbness of the tongue and lips, nausea, rapid heart beat, and muscle paralysis.