My favorite is: Daddy Longlegs are the most poisonous / venemous spiders on Earth, but their fangs are not long enough to penetrate human skin. Mythbusters tacked this one a while ago, as have many others. But seriously, how did it last so long? With so many of them around so many humans, and yet no case of injury? Come on. Any more you'd like to add? Chances are you'd be doing a good service.