Rock Smash

Rock Smash is Charizard's Side Special attack in which Charizard takes a large rock and headbutts it. The force of the headbutt has high knockback and very high damage. After this portion of the attack, the rock shatters into three smaller pieces that fly forward in a spread effect, dealing small amounts of damage. The attack is a powerful but slow finisher in normal matches. It is a useful move against bosses, as they do not make any effort to dodge the slow attack, and because they don't experience knockback, they can receive the maximum possible damage from the move as they can be hit by the headbutt and all the pices of the rock. In addition, since bosses are unaffected by knockback, this means every possible hitbox will connect, dealing massive damage, whereas playable characters will often be knocked out of range by the initial blow. Similarly, this means it is one of the few moves that can break a Smash Ball in one. It will take the full 43% damage, and break.

Origins
Rock Smash is a Hidden Move (HM) in the Pokémon games. It can be used in battle, and can also be used to destroy rocks outside of battle, similar to how the move "Cut" can be used as an attack in battle and used to cut trees and grass outside of battle. Rock Smash is one of the weaker damage-dealing attacks in the games, despite the fact that it is used to shatter very large boulders; however, it does have a chance of lowering the target's Defence stat, allowing more damage with subsequent attacks, and it allows some Pokémon access to a Fighting-type move.

Trivia

 * Whenever Charizard uses Rock Smash in the gloomy parts of the Rest Station in All-Star Mode, the rock will look like a chunk of ice.
 * While performing Rock Smash, any attack that interrupts Charizard will cause it to visibly drop the boulder. However, any attack that actually goes through Rock Smash's attack frames will simply make the boulder itself disappear, after the visible hit-lag.
 * Rock Smash is one of the most well known tips for getting through Boss Battles on Intense.