Terrifying sea worm.
This unsettling creature is called Eunice aphroditois, or colloquially the Bobbit worm. These critters can grow up to three meters long and have pincers capable of slicing its (sometimes larger) prey right in half. Also? It injects a toxin into its prey to make it easier to digest.
See video and read rest here: http://animals.io9.com/this-worm-is-truly-deeply-terrifying-1622516345