My favorite Shiny visually is definitely Shiny Mothim, closely followed by Tyrogue, Porygon2, Gallade, Corsola, Yanma, and Nidoran-M. I tend to like blue Shinies the most, but I also like a lot of pink ones like Dragonair, Furret, Jumpluff, Dunsparce, Celebi, Pachirisu, and Vanillite. I also really like Shiny Lapras, Quilava, and Luxio.
I dislike most of the green Shinies (excluding the Squirtle line's shells and Beedrill) like Onix and Dragonite, and the Shinies that have very little difference at all (excluding Persian and Glaceon) like the Togepi line and Garchomp.
Right off the top of my head, the Shiny I would most want to change is Avalugg. Those yellow jaw pieces really bother me. How about we just keep those white and make the only color difference the emerald filling?