Magnemite for High Tier. It is obtained in New Mauville, which coincidentally enough is right after you obtain Surf, and so the game moves into it second, very, very water-based half. It then proceeds to dominate Winona with the exception of Altaria, holds its own against Tate and Liza with the exception of Solrock's Flamethrower, and destroys Wallace/Juan, except Whiscash. But the way it handles the water routes so unbelievably easily is what makes it shine in my eyes.
The other electric types are Electrike, which is rather difficult to train until it has STAB, Voltorb, which sucks, and Pikachu, which comes afterwards but is OK I guess. Magnemite is the best in the game for my money. Shit movepool, but all it really needs is its electric move of choice.