IGN brings us a video that claims to have the rarest Pokemon one can catch in Pokemon Go. Like most Pokemon Go news as of late, it seems full of somewhat sketchy information. I'm not trying to dump on the video because I know some of it is very likely legit, but I have a friend who's never been in Austrailia and he owns a Khangaskhan so that makes me a bit leery of the info.
Other than that bit of info, the rest seems legit and I've heard from other places so I think it's solid enough to share with you.