I've found a few shiny's in G/S/C:
-(red Gyarados from 4 save files) Nothing special about these...
-was half awake. I thought I saw sparkles but I wasn't sure so I caught it just to make sure. And sure enough, it was shiny.
-Yay for hidden power: dragon. Yeah, it's an Unown... Found it while looking for something.
-wow, it's like sooo rare... caught it like 2 hours into a new file.
-lol I completely forgot about this little guy until just a few days ago when I found it in one of my boxes. Yay for another "rare" poke...
As for R/S, I have a shiny Flygon and Sandslash. Flygon was traded from my bro as a Trapinch, and I found the other as a Sandshrew by accident. At the time I was angry that I accidentally touched the grass