Actually, the Mantis Shrimp are said to have the best eyes in the invertebrates. The cephalopods have the best developed brains. That being said, cephalopods do have excellent vision.
A squid or an octopus.
A better answer for this question would be:
They are an invertebrate in the phylum Mollusca meaning "soft bodied" (Mollusks). The class Cephalopoda means "head foot", meaning...