This marks the first time Gigantamax Pikachu was found in Max Raids.
This Pikachu has the move Volt Tackle, which is normally only available by breeding (while parent holds Light Ball).
Volt Tackle also cannot be passed from breeding parent to breeding parent, unlike other egg moves.
Note that the Gigantamax factor cannot be obtained by breeding, thus this combination (Gmax + Volt Tackle) is normally not possible.
This also marks the first time Gigantamax Pikachu can be shiny, as the only one previously available was shiny locked.
The Wild Area Event for this Pikachu can be found here.