I shall do a couple more because I'm bored haha
Tangrowth (A Rank)
Obtainable: Before Gym 2 or 3 (can't remember exactly...) (Shadow)
Abilities: Always go for Regenerator unless you're running a Sun team... but I still think Regenerator would e better
Moves: Giga Drain, Knock Off, Wild Charge, Ancient Power, Sleep Powder, Power Whip, Sludge Bomb , Leech Seed (breed)
Useful For: Boss Battles, Marianette, Valerie
Summary: Tangrowth is a pretty useful Pokemon to have. Its base 125 Defense is nothing to be scoffed at, and with access to a range of decent physical and special offensive moves such as Knock Off, Wild Charge (surprise surprise), Power Whip, Ancient Power - it hits pretty hard too. It is also capable of learning recovery moves such as Giga Drain and Leech Seed - and its ability allows easy HP recovery upon switching out.
The downside of Tangrowth is its abysmal special defense and speed - so don't be surprised if it gets OHKOed by a special fire or bug move. Hence, it is pretty helpless against Angie and Amber. It does help against Valerie to some extent (I would recommend giving it Quick Claw) but watch out for those Ice Beams.
Magneton (A Rank)
Obtainable: Before Gym 6
Abilities: Sturdy and Analytic are both decent.
Moves: Charge Beam, Discharge, Flash Cannon, Metal Sound, Thunder Wave
Useful For: Boss Battles, Angie
Summary: Although Magneton doesn't have access to a wide movepool, STAB Flash Cannon/Discharge will be quite painful. If the opponent gets hit by Metal Sound before that, it will hit harder. Thunder Wave is always useful to have - as speed control is pretty important and Magneton is pretty slow itself.