And that's why it is beautiful, I mean I would use Mega Steelix(loved Steelix, the mega is everything I love of Steelix made even better) Slowbro(Mega or not), Beheyem, Jellycent M, Tentacruel and Gengar, Skarmory, Scizor, Weavile, Darmanitan, Blastoise, Meganium, Sceptile, Infernape, Serperior, Delphox, Chesnaught, Staraptor, Talonflame, Yanmega, Starmie, Chandelure, Bronzong, Heatran, Scolipede, Mawile, Aerodactyl, Sableye, Metagross, Hippowdown, Gyarados, Tyranitar and Mega Diancie left and right if I had the choice. Those are great Pokémon niche wise and had great utility in ingame runs making me love them... Heck half of them are OU and boss at it.
But synergy is more important competitive wise. And I just realized that outside of Kyogre, Spheal, Chimecho registeel, and sharpedo I don't really dig the gen 3 designs, yes I mentioned around 4-5 of them top but I had to think hard on gen 3 stuff... I had to go all the way to remember those...and I love water types...