My Meowstic has got quite a lot of work done. STAB psychic is always great, plus learns shadow ball, which helps a fair bit. Just bought an abra, and alakazam is probably better once trained up, but Ive been very happy with Meowstic up until now.
One thing ive noticed is its difficult to get a decent moveset. Ive finished the 9th gym and still havent found many useful TMs.
Charizard has been nice and Ive been fairly reliant on him to get me through the game, but I wish I had started with a water pokemon. Cant seem to find a decent one, yet fire pokemon seem abundant. Growlithe has always been one of my favourites and was surprised you can get him so early, he turns into a beast.
Looking through the pokemon Ive caught and could have potential, I know Flygon can be pretty decent. Anything with half decent attack, speed, and learns STAB earthquake.... thats always going to be powerful.