If you ever find yourself in central Africa, here's a piece of advice: don't mess with the frogs. As Ed Yong over at "Not Exactly Rocket Science" warns us, several species of them come equipped with a set of bony Wolverine-like claws that punch through their skin when threatened.
Nature's full of clawed animals, but the frogs' defense mechanism is unique in the natural world because their claws literally rip through the skin when extended. They're also made of bone instead of keratin (sorry, no adamantium claws are known to exist in reality, except for this guy). Researchers aren't sure if the claws are retractable or not, and as Yong notes, they may never really want to find out: