Sigilyph and Steelix are tied for my favorities. Sigilyph is colorful and the colorscheme turns into this really neat looking orange and green type of thing, and as for Steelix it turns golden. Shiny Mega Steelix is a beautiful sight to behold. I've been lucky enough to obtain both of these shinys, currently sitting in a box full of other shinies in Omega Ruby waiting for bank update day.
I love the shiny appearance on Fennekin and Decidueye. For Fennekin, I love the way the gray, red, and white mixe in with it. For Decidueye, the colors on it shows more character like of robin hood on it and that really touched me a bit.
Well, there's my username for starters. Lol. But seriously, I think my actual favorite is shiny Aegislash (here are the images for its shield and blade formes). I think the black and gold look amazing together, and the red is a nice accent that emphasizes the more bloody nature of a sword (especially as a Honedge). All in all it just looks super cool
I really like the colors of Shiny Aggron. But shiny Linoone is my favorite, because it was the first of the two shinies that I found, and it actually looks pretty neat.
Hmm. Not quite sure! Skarmory's is quite nice, I guess? Oh! And Nidoking's Nidoqueen shiny paint job swap is pretty neat too! I kinda wish Nidoqueen's shiny form was pink too instead of that garish dark green colour, haha.
I have a tie for favorites, Mew is one, the shiny Mew card was my first Pokémon card so it holds a lot of value and love for me. In DPP my friend gave me a shiny mew he got from another friend, it was named (regrettably though I grew to like the name as time went on) Bastrido . I got it every ribbon in DPP, I think it is still trapped there In end, I loved the shiny and the Pokémon deeply. The other is Sylveon, I love the pink but the blue is very shining and stunning on it, I don't think it has great stats but I have trained it very hard because I enjoy the Pokémon so much as it but the shiny is so nice. I really like Shiny Garchomp for when it mega evolves it turns PINK! I love the color pink and I think it looks killer in the color.
Shiny Emolga because it's all golden...and I just absolutely love Emolga! (if I were to have Ash catch an Emolga in a fanfic...it'd be Shiny...just too cute!...not saying [3D='Emolga'] isn't cute too). Shiny Victini having a white body instead of yellow (not trying to stir up racism, just pointing out something else...) is kind of cool, but I still really love regular Victini ([3D='victini'] ) too, don't get me wrong... Like with Emolga, both forms are equally cute, adorable and awesome!
Some people pointed out some of my personal faves like victini , zorua and rowlets lovely line ( i like the whole line so yeah ) I do love I have many many more but here are some top faves.