Skull Bash

Skull Bash is a move that both Pikachu and Pichu know in Super Smash Bros. Melee. It is executed by pressing Side+B. Once done, Pikachu or Pichu will pull their heads back, and then push forward into the opponent with a headbutt. The player could hold down on the B button to charge the attack. This will make the attack stronger, and will make it more accurate. Sometimes, Pikachu or Pichu will even be able to fly completely across some stages, like Pokémon Stadium or Green Greens. If the player charges the attack to its limit, than Pikachu or Pichu will use the attack automatically. The attack can also sometimes. it is unknown if Pikachu will use this attack in Super Smash Bros. Brawl. Pikachu's Skull Bash can charge faster, but his attack and range are slightly shorter than Pichu's. However, Pichu's Skull Bash takes longer, but can go farther and is stronger at maximum power.

Trivia

 * Despite the fact that Pikachu and Pichu can indeed use Skull Bash in Super Smash Bros. Melee, he has never been seen executing it in any of the Pokémon games. Although, this may be a reference to the Pokémon move Headbutt, a move Pikachu and Pichu can use.
 * This attack is very similar to the Green Missile. Even one of Luigi's trophies states that Luigi's Green Missile move is similar to the Skull Bash.