Most recently (about 4 or 5 days ago), I found a shiny Gulpin in a horde while EV training my shiny Larvitar. :P I figured that, eventually, I would find a shiny while EV training since I hear about it happening to so many people. Excluding the Friend Safari, it's also pretty cool because this was my first random shiny in the wild since my shiny Tentacool from Chrono Island in FireRed (my very first shiny!), and that was a LONG time ago.
I've successfully hunted two shinies in the Friend Safari (Metang and Phantump, crazily both the pokemon I wanted), but I've also found shiny Combee one time when I was fetching some parents for breeding and a shiny Pumpkaboo on Christmas Eve, though I have no clue what I was doing in there at that time. :P
And finally, though not entirely as accidental, I found a shiny Skiddo on a chain of 23. What made it crazy, though, was that I was in the middle of MM'ing for my shiny Rotom which is my longest hunt yet (right now 1200 eggs and I still haven't finished it, but I took a huge break to get the Shiny Charm), but I wanted to see if I'd have any luck elsewhere. I had never actually reached a chain of 40, but I reread some tutorials and I thought I was ding pretty well. And then out of nowhere, shiny patch at 23. I caught my shiny Skiddo (who was Adamant thanks to my Synchronizer) and, because I didn't realize that the chain stops, I kept going and actually made it to 39! I purposely broke it then because that was when I found out. Goes to show how insane the RNG is.
I'm pretty jealous towards the people who find non-MM shiny babies, though. That must be really cool.