Octopus
The octopus has one of the most interesting nervous systems in the world. The octopus is arguably the most intelligent invertebrate. It has a complex nervous system, and it's fantastic brain is just the tip of the iceberg. Two-thirds of the octopus' neurons are found in their arms, giving the, a limited autonomy. It would be like your arms being able to function on their own. Their arms have been shown to react to things, even without any signals from the brain.