Here's a list of my shinies that I have or have had besides Gyarados in HG/SS:
-Emerald: Koffing
-Platinum (lost): Roselia, Sneasel, Marill, Blissey
-HeartGold (lost): Mewtwo
-SoulSilver: Tentacool, Golbat, Nidorina
-Black: Gothita
-White: Sewaddle, Golduck, Vulpix, Lunatone
-White 2: Petilil
-Black 2: (will add when I pick up the game again; I can't remember atm)
-X: Nosepass, Drifloon, Wingull, Mawile, Clawitzer, Bibarel
-Y: Pikachu, Luvdisc
A few weeks ago, I ran into a shiny Riolu in Y. I only had 2 shots at catching it, and I failed, even though its HP was in the yellow and it was paralyzed.