i did once in SS. my little sister found a shiny Volbeat in the Bug Catching contest. it was LV34 and it kicked her Chansey into kingdom come. she then caught a Nidorino a couple of days later and also caught a shiny Machoke in 1 week apart. i said i was going to find one too! a couple of weeks later i went Entei hunting. i found a shiny Raticate. at least it wasnt Bibarel ._.
I caught my first shiny (didn't hunt it just appeared) in SS too, and it was a Raticate as well haha.