The newest addition to the shiny Pokémon pool in Pokémon GO has been confirmed to be Snorunt. Snorunt and 21 other Pokémon including Delibird have just been added to the game as part of the Christmas event. No other shiny sightings have yet been made.
Meanwhile, it has been discovered that Wailmer requires 400 Candy to evolve into Wailord, much like Magikarp. Feebas meanwhile requires both 100 Candy and to be walked for 20 km as a Buddy Pokémon prior to evolution. The game at least shows us this requirement now.
Lastly, Delibird grants 250 stardust when caught (far more than usual), and Lures appear to last for at least a couple hours during the current Christmas event. Lastly, Starter Pokémon (including Mudkip, Treecko and Torchic) may be more common already.
Have you found any shiny Pokémon in Pokémon GO yet?