Release Dates:

Global: November 18th 2016 - January 11th 2017

If you load up the game and go to Mystery Gift before January 11th 2017 then you can download a Munchlax. This Munchlax is special in that it comes with a Z Crystal

Munchlax ♂/♀ Level 5	OT: Yours ID: Yours Ability: Thick Fat Hold Item: No Item	Any Nature. Date of Receiving a lovely place. Apparently had a fateful encounter at Lv. 5	Tackle Metronome Hold Back Happy Hour
		This event also comes with the gift of a Snorlium Z.

Release Dates:

Europe: July 13th 2017 - August 14th 2017

To coincide with the release of the Shiny Tapu Koko Premium Collection TCG set, the special shiny Tapu Koko was made available over Mystery Gift via Internet

Tapu Koko Level 60 ★✚

OT: Melemele ID: 170714 Ability: Electric Surge Hold Item: Electric Seed

Timid Nature. Date of Receiving a lovely place. Apparently had a fateful encounter at Lv. 60

Nature's Madness Discharge Agility Electro Ball

Release Dates:

Europe: March 1st 2018 - March 24th 2018

Method:
As the second month in the year of Legendary Pokémon, Regigigas was distributed to Ultra Sun while Heatran to Ultra Moon, allowing you to get the Legendary Pokémon not in your version.

Regigigas Level 60 ✚

OT: ?? ID: 2018 Legends Leyendas2018 Légendes2018 Legenden2018 Ability: Slow Start Hold Item: No Item

Any Nature. Date of Receiving a lovely place. Apparently had a fateful encounter at Lv. 60

Zen Headbutt Revenge Dizzy Punch Confuse Ray

Heatran ♂/♀ Level 60 ✚

OT: ?? ID: 2018 Legends Leyendas2018 Légendes2018 Legenden2018 Ability: Flash Fire Hold Item: No Item

Any Nature. Date of Receiving a lovely place. Apparently had a fateful encounter at Lv. 60

Crunch Scary Face Lava Plume Fire Spin

Release Dates:

Global: January 8th - September 2nd 2019

Method: The previously unobtainable berries of Enigma Berry, Micle Berry, Custap Berry, Jaboca Berry & Rowap Berry were distributed in the final year of Generation 7. This gift comes with 12 of each Berry