Other than the red Gyarados in Lake of Rage, I haven't caught a shiny Pokemon yet on SoulSilver. Though, I have traded a few shinies from my Diamond onto SoulSilver. They include a silver metagross, a brighter yellowish (XD) Hariyama, a black Charizard, and a black Rayquaza.
May make random appearances every-so-often. Trying to officially return...
POKEMON BLACK FRIEND CODE: 1249-2602-6566
POKEMON BLACK2 FRIEND CODE: 1679-1583-9820
POKEMON Y FRIEND CODE: 3308-5051-2299