Seriously. Isn't that just incredible? Doing a Google image search on these is like confectionery for the eyes.
You may have heard of it before - this entry is about nudibranchs, more commonly referred to as 'sea slugs'. They're smallish marine creatures with striking colouring and a truly awesome defence mechanism.
Nudibranchs like to chow down on (amongst other things) sea anemones. This is significant because sea anemones have their tissues filled with little stinging buds called nematocysts, which are what anemones use to poison any prey that happens to get too close. And under normal circumstances, by all rights the nudibranch should be killed from eating anemones.
However, sea slugs have evolved the capacity to swallow these poisonous, stinging cells and remain completely unharmed by them. In a way, it's as though the nematocyst is a bomb, which the nudibranch manages to diffuse.
But better still, the nudibranch then absorbs these nematocysts into its own tissues - and then uses them to defend itself against predators. Sort of like taking a weapon from someone who was about to hurt you with it, saying "Thanks for that!", and then proceeding to use that weapon against someone else you didn't like.