Cone Snail
It seems impossible that two snails could hold a place on this list, but cone snails are not to be trifled with. Cone snails tend to lurk in tropical regions of the world. While they’re beautiful to look at, with their elegant white and brown marbled shells, they’re toxic to humans. They have harpoon-like teeth that have conotoxin, a neurotoxin that is incredibly dangerous to humans, as well as a concoction of many other toxins. There are about 600 species of cone snail, all of which are dangerous to humans. Their stings occur without warning, and because there’s no antivenom, their stings can be fatal. The toxin works by stopping communication between nerve cells.

Symptoms include numbness, tingling, intense, uncomfortable pain, paralysis, blurred vision, and respiratory paralysis. If you do happen to get stung by a cone snail, you must go to the emergency room immediately to receive proper treatment before it’s too late. Out of all the species, the geographic cone is the most venomous one. There have been several deaths reported from this cone snail alone (Flamingoof).