Mine was a Litwick in Black 2. I'd planned on shiny hunting which is kind of what made me really get into the pokemon games, but this one I found while EV training my Umbreon during my playthrough, so it was a complete surprise.

Currently, it sits in my PC box. I don't really like Litwick/Evos much, but I do like the shiny form a lot more...Except that as a Chandelure, it's fire and eyes turn to regular fire colors...Lame =.=