Had lots of shinies from my old G/S/C games. There was a trick on getting a blue ditto which involved using a shiny gyarados that only knew mimic and that produced a 1 in 256 chance of hatching a shiny pokemon too.
All of these are in the Advanced games, mind you.
I didn't have much luck in G/S/C, the only Shiny I ever caught besides the Shiny Gyarados was a Caterpie, now Butterfree, named Papillon. Though I did see a Zubat, I killed it >.>
I only have 2 of them and im so lucky. Literaly i am luck. o.o;
I have a shiny Sandslash and a shiny Golbat.
Got the Sandslash from sapphire and Golbat from a friend from Victiory Road.
I had every shiny pokemon back in GSC But cant discuss how, im sure you all can figure it out.
Now i caught a shiny Ralts in my first Sapphire game. He's now a Gardevoir. Shiny Gardevoir looks cooler in Col/XD since its purple. The Ralts was the only shiny pokemon ive seen in all five of the GBA games i have. I was shocked to find it in the first place.