The goal of all this misery is to make predators and enemies stay away. The slow-moving Gila monster can become easy prey, and it relies on its knack for a nasty bite to defend itself.
While the Gila monster's venom might have caused misery in a few people, it has ended up helping many others; it's now the source of a new drug, called Byetta, which treats type Type II Diabetes. Researchers believe that this drug is just scratching the surface of the potential that venomous species have — each creature in this list produces complex, potentially lifesaving compounds.
Something to keep in mind next time you curse the existence of that pesky bee or sneaky snake.