Electrical Mimicry – The being has a body composed of electricity.
Electro (Marvel) is a supervillain that started out with a human body but is now made out of electricity and therefore much more powerful.
Livewire (DC) also has a body made out of electricity but seems to have electrical versions of human organs.
Zzzax (Marvel) is made up of pure electricity (Official Handbook of the Marvel Universe V1 #12).
A being of pure electricity in Out of the Night #11 (ACG).
Amaak is a being of pure electricity that fights the Herculoids in Hanna Barbara Super TV Heroes #6.
Minion of Karakal – Field Guide to Creatures of the Dreamlands
Storm Elemental – D&D 3.5 – Monster Manual III
Megawatt – Cyberforce-Sourcebook #2