Mantis shrimp, from the order Stomatopoda, are not actually shrimp, which belong to the order Decapoda. Mantis shrimp are generally divided into two basic groups: those that spear their prey with powerful strikes of a spear-like foreclaw and those that smash prey with a blunted foreclaw. In this video, the two Lysiosquillina species are spearers and the Odontodactylus, or "peacock mantis shrimp", is a smasher. The striking claw of a mantis shrimp is so powerful that the friction caused by the claw pushing through the water generates so much heat that the water actually boils.
However, rather than the claws, the most "striking" feature of mantis shrimp may be the eyes. On independently mobile stalks, they can achieve nearly 360-degree vision. By virtue of the arrangement of optical cells in the eyes, mantis shrimp can perceive depth with just one eye. While the human eye has only two types of photoreceptors, mantis shrimp have eight, meaning they can see color a much greater range of color than we can, into the infrared and ultraviolet realms of the light spectrum. They also have eye cells specialized for detecting polarized light, and it has been shown that mantis shrimp have means of communicating with others of their species through color signals which can only be detected by seeing polarized light. This ScienceBlogs post has more details.
But I CAN't tell the story of the mantis shrimp in a more entertaining fashion than The Oatmeal! Click the image below to check out this amazing infographic: