Duck-Billed Platypus
The platypus is one of the few mammals that lay eggs. It is also one of the few that are venomous. The male duck-billed platypus can deliver a mighty sting that causes immediate pain to any intruder. The pain is described as hundreds of hornet stings at one time.
Scientists have said that the method seems to be used only as a defense mechanism. The production also tends to rise during the breeding season, so several experts believe it is used to assert dominance and control the territory.