The first shiny i encountered on X by accident was an Ursaring, i was looking for an Altaria for my dex, but the first poke i found on that route was a shiny green Ursaring, catched him obviously, but dont liked so much so i traded for a shiny granbull, wich i finally traded for a... i dont remember what i think a legendary XD
The second shiny found by accident, it was when i was looking on the friend safari for a 2IV ivysaur to start breeding one, again the first poke i found there was a shiny sunker, i still have it but i dont want it, and seems like no one wants it too XD
And the third accidental shiny was a shiny Alomomola, i was looking to fish a clauncher for the dex, and again the first fishing was a shiny Almomola, again i dont like it, i dont want it, and no one wants it XD
Ive been pretty lucky with this shinys, but whenever i try to find any special shiny poke, i never get it :/