10. Jellyfish Sting
https://www.youtube.com/watch?v=7WJCnC5ebf4 Jellyfish stings are, at best, a day-ruiner and, at worst, a death sentence. The reason they're so painful is that they are actually stabbing you with a bunch of microscopic needles and injecting venom into your skin. We don't know exactly how a jellyfish deploys these little needles of pain, but we know that it will do it if we run an electric current through it. The needles fire out and the venom is released after a short time. Skip to 2:12 for the actual sting footage, but if you want to see a very excited Australian scientist nerding out over this stuff, watch the whole thing.