Leader of Jigglypuff Army
Some of them have different moves. I know that the Hoenn and Sinnoh hats have Iron Tail and Unova has Electro Ball. Kanto has Thunder and Thunderbolt but I'm not sure which one is the Kanto exclusive. That one really has no special move set and is the only one that is a normal Pikachu but with a hat. The main site has info.Any of them can use 10,000,000 Volt Thunderbolt. Besides starting level, I don't think there's any difference between the different hat Pikachus.