I'm not going through the entire thread to see if this pokemon is listed, so I dunno if it's been mentioned or not.
But, I run nuzlockes often, and when I did runs of X/Y...if Chatot appears outside Shalour City (Route 12), forget it.
The thing has a capture rate of 30% (which is lower than Xerneas, btw), but it feels even lower. I'll get its HP down to the red, and use the best pokeballs I have at the time, and it'll still bust out. I lost out on a capture on that route on two separate nuzlockes because I ran out of pokeballs, great balls, premier balls...everything I had just trying to catch that gosh-darn Chatot.