Pfeffer's flamboyant cuttlefish
Don't try to cuddle this cuttlefish. Though charming and colorful, this aptly named fish's displays are meant as a warning. Like octopuses and some squid, cuttlefish are venomous. The muscles of the cuttlefish contain a highly toxic compound.
Although cuttlefish rarely encounter humans, their poison is considered extremely toxic and can be as lethal as the poison of the blue-ringed octopus, reports MarineBio.