3. Flesh Eating Bacteria -
We couldn’t show you a picture of this stuff in action, because you’d yak up your lunch and have nightmares for the next gazillion years. Otherwise known as necrotizing fascitis, this ultra-rare but oh so deadly bacteria creates an infection deep within your skin, and a significant delay in surgical treatment means certain death. Heck, even if you do treat it, you're almost certain to lose whatever limb is unlucky enough to come within contact with it.