Dodrio is Kanto's best offensive normal flyer. With tri attack and drill peck, they have two great physical STABs, to fully exploit that high speed and attack. Doduo can be picked up right before getting Fly, so it flows nicely as well.
Crobat would be good as well, but in my experience Golbat refuses to evolve before the national Dex is acquired. Golbat goes into an evolution animation and then... stops. Doesn't break the game or anything but you can't count on Crobat.
And if you don't mind legendaries: Zapdos is available relatively early and very powerful.