Puffer Fish

Puffer fish are hilarious and adorable just on general principle. It's hard see one inflated, and refrain from uncontrollable giggling at it's cartoonish defense mechanism. But puffer fish don't just rely on their inflatable belly as a way of dissuading predators, they're also packed with the deadly neurotoxin tetrodotoxin. Of course, they're renowned as a delicacy just for this reason. Apparently, when prepared correctly, the minute traces of the toxin give you tingly lips and light-headedness. However, if the sushi chef doesn't prepare it properly, you're going to have a rather nasty death. See, tetrodotoxin is a muscle paralyzer, with no known cure. So if you overdose, your muscles no longer move, including your diaphragm. You become paralyzed, and unable to breath, slowly asphyxiating under the weight of your own chest.
http://brainz.org/15-cute-animals-will-cause-you-horrible-harm/