Originally Posted by Fat Lucchini
I'm thinking Weedle/Beedrill could go up. Bug-type moves are super-effective against poisons in this gen, so that's 4x effective against the common grass/poisons and nearly everything in Erika's gym.
It also learns Agility and Swords Dance. When up against Sabrina in Yellow, use Agility once then tear through everything with Twineedle. Far more reliable than most others strats you can think of.
You're also agreeing upon Psychic-type's exceptional value, which I assume has more to do with the poison-type being everywhere than 30% likely special falls or absence of dark/steel types and ghost moves.
But that's exactly the point. Psychic gives amazing coverage. Nothing in the game resists it aside from other Psychics. So help you if you are weak to it as well, as most of the pokemon that pack Psychic are dangerous (Alakazam, Exeggutor, Starmie). Psychic-types are so broken in RBY that being one is an outright advantage. Of the 2 moves in the game that they are weak to, one is on Beedrill, and the other is on Jolteon. And it's worth noting that they aren't exactly accurate reliable moves.
And Beedrill is definitely low. It has some good points, but aside from Rocks and Waters what doesn't beat Erika? And also, it does not beat Sabrina just because it has STAB Supereffective twin-needle. You have to remember, all of her pokemon carry Psychic-type moves (3 of which have STAB on it). The pokemon you would need to use Agility on would be Kadabra who has STAB Psybeam and Psychic (and will use it because the computer is programmed to use Supereffective moves). Let me put it this way, Kadabra will be faster than Beedrill. Remembering Beedrill's Special is terrible, and Kadabra's is awesome, and knowing Kadabra is likely to crit, at what opportunity will Beedrill get to use Agility? For this to work, Beedrill has to be significantly overlevelled.
You have to remember that Beedrill is weak to so many types. Flying, Fire, Rock, Psychic, and these types are everywhere. He is only resistant to Grass (who isn't?) and Fighting (no offensive presence). Keeping that in mind, his frailty combined with his lack of any decent moves means that even if he is getting an Agility off, he won't be doing much but poking whatever comes his way.