Besides the Red Gyarados of course, it was a tentacool.
Yeah, I caught it in Leafgreen. I knew nothing about shiny back then, so I though it was a special tentacool that could be found at this spot. (It was on an island, the one with Moltres I think). So yeah... when I restarted my game, I returned there and tried during hours to find the damn special tentacool. Then later I found out about shiny pokemons. FUUUU---
That was the only one up to date, I'm really unlucky haha xD