Self-Destruct

Selfdestruct is a Normal type move. Pokémon that can learn this booming move are Geodude, Graveler, Golem, Voltorb, Electrode, Koffing, Weezing, Pineco, Forretress, Baltoy, and Claydol.

It has a more powerful version called Explosion.

In Battle
As the name states, the user explodes, causing he/she to faint. This attack is devastating and can cause massive amounts of damage to every other Pokémon out.

Only ghost typed Pokémon are immune for the move.

If you received the Winner's Path for the Pokewalker in Heartgold and Soulsilver, you can find a Muchlax that knows Selfdestruct.