https://www.gamespot.com/articles/last-free-pikachu-for-pokemon-sun-and-moon-availab/1100-6454333/

Pokemon Sun and Moon players who have yet to add Ash's Pikachu to their team have one last chance to claim the special Electric-type mouse. The Pokemon Company is distributing the last of its six free Pikachu from now until October 30, this one wearing Ash's cap from the Alola region.

As before, the Alola cap Pikachu has a Hardy nature and comes with its exclusive Z-Crystal, Pikashunium Z, which allows it to use the 10,000,000 Volt Thunderbolt Z-Move once per battle. It also knows the following four attacks: