RE: Pokemon Best Wishes Episodes
Well there have been times where more than four moves have been used, Electivire in the sinnoh league used, Brick Break, Thunder, ThunderPunch, Protect and Giga impact, as well as Heracross using more than four moves, and the most recent example, Ishizumai.
I think all of Pikachu's moves are valuable, in their own ways, but if he did get rid of one, I'd say volt tackle, or Quick Attack. Volt Tackle because, Pikachu has a new way of using thunderbolt this season, and it's one it's oldest moves, Quick attack got a new animation, so did Iron tail, but I don't think Volt Tackle got a makeover, but Volt Tackle is a better Quick attack in my opinion, so either those two, if he gets rid of a move.