4. Cone Snail
One might not think that a snail is particular dangerous, but the Cone Snail is actually venomous. One drop of the Cone Snail venom is enough to kill 20 adult humans.
There’s no anti-venom for the Cone Snail – and it’s otherwise known as the “Cigarette Snail”, because they say that once you get stung by the Cone Snail you have enough time to smoke one cigarette before the venom gets to you.