Electrtic Types
Electic Types are super effective against Water Types and can put Water Types at a disadvantage. This is because Water Types love to use Rain Dance which will give Thunder an accuracy of 100%! Electric Types are generally faster than most other types, but watch out for those ground types. Electric moves will not work at all against rock types and will most likely faint after one Earthquake!
Electabuzz is a fairly good electric type and is found in the Power Plant in Pokemon FireRed. Electabuzz doesn't evolve and is somewhat rare.

Jolteon is a very fast Pokemon and can KO many Pokemon which it has a disadvantage over with one move, Thunderbolt. An example of this is Aerodactyl(and Salamance though this is rare). Aerodactyl and Salamance carry Earthquake(most likely) and would one-hit KO Jolteon if it didn't KO Aerodactyl first. But Aerodactyl has flying traits so Jolteon can launch a super-effective Thunderbolt to KO Aerodactyl. Watch out for any physical attacks because Jolteon might faint after a few of those. And if you didn't know, Jolteon evolves from Eevee, which can be found in the Celadon Mansion.

Manectric is a pure electric type as are all of the Pokemon on this page. Manectric evolves from Electrike and can be found in many places in Pokemon Ruby/Sapphire/Emerald so check your Pokedex!

Plusle is a great companion to Minun with its ability and has high attack. It learns Quick Attack and Shock Wave which makes a great combination in the Cool Category. Plusle can be found in Pokemon Ruby/Sapphire/Emerald in the roads above Slateport City.

Minun is similar to Plusle and is very fast.