Killer cone snails

Some cone snails send fish to sleep with sedatives before they kill and eat them, some stun them with a shock of nerve-toxin, some kill them outright with a cocktail of poisons, so toxic there are at least thirty cases of humans dying after picking up these sea-snails.

The cone snails have evolved toxins so deadly, so specific and so varied that they have provided neuroscientists with a cornucopia of chemicals to investigate the workings of nerves, their connections and transmitters, and the basis for drugs such as the pain-killer Ziconotide.

Read more here: https://www.understandinganimalresearch.org.uk/news/staff-blog/how-snails-hunt-fish/

and here: http://www.animalresearch.info/en/drug-development/venom-derived-drugs/