Meet the spider-tailed horned viper, native to western Iran. As the name suggests, the snake has a tail that, when moved about in the right way, looks like a spider crawling on a rock. The crawling "spider" attracts small birds who eat insects...and then the viper eats the birds:
Sweeeeeeet Fancy Moses! If an animal with venomous snake jaws on one end and a spider on the other isn't everyone's idea of a nightmare animal, I don't know what is.
But what an incredible evolutionary adaptation. This mimicry is right up there with the bee orchid. (via @jasonfried)