Thunder

Thunder is a move used by both Pikachu and Pichu in both Super Smash Bros. Games. To perform it, one must press Down+B, which will cause Thunder to drop down onto the screen. It will fall onto Pikachu or Pichu, and will hurt any player that touches the lightning. Luckily, it doesnt hurt Pikachu, but it gives Pichu around 2 damage when doing this move. If Pikachu or Pichu is jumping when the attack strikes, it will not hit underneath them. It is Pikachu and Pichu's strongest move, in both Super Smash Bros. and the Pokémon series. The move will return as one of Pikachu's attacks in Super Smash Bros. Brawl

Trivia

 * A Thunder move is also used by Marylin in Paper Mario: The Thousand Year Door.