Vampire squid. (Spiky tentacles. Toots bioluminescent ink.)

Siphonophore (Search through the sub for this one.)(If unique is what you want, you want this guy.)

Cone snail (Shoots poison harpoon. You could poon an orca in the butt.)

Hagfish (Devourer of the dead. Excreter of suffocating slime.)