Today Niantic started their Special Battle Showdown, and has released 4 new shiny Pokemon; Meditite, Medicham, Makuhita, and Hariyama.
Thanks to those that were the first to provide screencaps, and special thanks to /u/Freshie97 for specifically evolving the shiny Medicham for us.
Check out these additions and the addition of Zapdos on our Pokemon Go Pokemon Releases page.