Penetrate! (つらぬけ!) is a rush attack used by Goku. While the opponent is in the air, Goku charges a one-handed Kamehameha and fires it at the ground to launch himself up into the air. Then, he shouts, "I'm going to put everything I got into this move!" and clenches his hand into an energy-powered fist. A silhouette of a Great Ape (which is said to represent Goku's hidden powers) appears as Goku puts his fist forward and punches through the opponent, inflicting a huge amount of damage.
Goku used this attack to defeat King Piccolo. After breaking Goku's legs and left arm, King Piccolo flew high up into the air and charged back down to kill the crippled Goku. However, with his right arm still intact, Goku launched himself up at King Piccolo with a Kamehameha and attacked him with the "Penetrate!" punch. Although King Piccolo braced for impact, the force of Goku's attack was too powerful and the evil Namekian was left with a large, gaping hole in his chest. However, King Piccolo spat out the egg of his final offspring and reincarnation and encouraged his son to avenge his death by killing Goku before succumbing to his injuries and blowing up. Goku later used the "Penetrate!" punch when fighting Mr. Popo, though Mr. Popo effortlessly dodged it, much to Goku's shock.
"Penetrate!" was named in Dragon Ball Z: Budokai Tenkaichi 3 and is Kid Goku's Ultimate Blast. It was also named "Super Dragon Fist" in Dragon Ball Z: Budokai 3 and "Punch Through!" in Dragon Ball: Advanced Adventure.
Prior to his battle with King Piccolo, Goku used a similar technique to destroy the Red Ribbon Army Battle Jacket which the recently self-promoted Commander Black piloted, resulting in Black’s death. This attack was the same as Penetrate! but with two hands extended forward, rather than one (probably since Goku had no usage of his other limbs at this point when fighting King Piccolo). When reflecting on the events of the Red Ribbon Army war, Master Roshi referred to it as Goku "using his head."
Gohan also used a technique nearly identical to Goku's attack on Commander Black to rip a hole in Garlic Jr.'s body followed by blasting him with a Masenko. However, since Garlic Jr. was immortal, the attack barely phased the demon.
The techniques Dragon Fist and Super Dragon Fist, are believed to have been derived from the Penetrate! technique. In Dragon Ball GT, Goku used the Dragon Fist to defeat Super 17 in a similar fashion to the way he killed King Piccolo decades earlier (by ripping a hole through the chest). Although the "Penetrate!" punch was strong enough to cause King Piccolo to explode, Super 17 was able to survive the Dragon Fist and it required a Kamehameha from Goku to finally finish the super android.