Venomoth, Pinsir, Ledian, Yanma, Forretress, Shuckle, Nincada, Ninjask, Shedinja, Illumise, Kabuto, Kabutops, Omanyte, Omastar, Aerodactyl, Anorith, Armaldo, Murkrow, Sneasel, Tyranitar, Sableye, Carvahna, Sharpedo, Absol, Vibrava, Lanturn, Electrike, Manectric, Primeape, Hitmonchan, Tyrogue, Breloom, Makuhita, Ninetales, Ponyta, Rapidash, Quilava, Numel, Camerupt, Doduo, Natu, Xatu, Jumpluff, Delibird, Misdreavus, Shuppet, Banette, Duskull, Exeggutor, Sunkern, Lileep, Cradily, Cubone, Marowak, Piloswine, Wigglytuff, Lickitung, Blissey, Kangaskhan, Porygon, Porygon 2, Girafarig, Granbull, Stantler, Smeargle, Exploud, Delcatty, Zangoose, Castform, Qwilfish, Drowzee, Hypno, Ralts, Kirlia, Gardevoir, Slowking, Grumpig, Claydol, Sudowoodo, Nosepass, Relicanth, Mawile, Feebass, Huntail, Gorebyss....
....give or take a few others who I've probably forgotten. Most of those are for general screentime, but there are still a lot of regulary seen pokémon that are yet to be used in a decent battle. Ursaring and Electrode spring to mind.
Though, if we're talking about the pokémon in each of the main character's possession...
Ash needs to use Torkoal, Glalie and the rest of his Catch n' Oaks, which is a redundant no-brainer these days.
Haruka needs to be using 'shamo a lot more than she does, as the rest of her pokémon already get decent enough screentime.
I don't care if Brock uses his pokémon for battle as long as they do SOMETHING.
Jessie should bring out Dustox a lot more, and use Wobbuffet as a battler.
Thats about it.