Rock Smash (いわくだき, Rock Smash) is a damage-dealing Fighting-type move introduced in the second generation. It was TM08 when it was introduced, and became HM06 in the third generation, as its use became essential for completing the game. It lost its HM status in the fifth generation, where it became TM94.
Outside of battle
Rock Smash is able to destroy cracked rocks.
By leveling up
Super Smash Bros. Brawl
In Super Smash Bros. Brawl for the Wii, the Pokémon Trainer's Charizard can use Rock Smash as its special side move. In Super Smash Bros. for 3DS and Wii U, Rock Smash became Charizard's down special.