Electric Kamehameha is a golden version of the Super Kamehameha technique used by Gohan and Goku.
First, Gohan charges up an incredible amount of ki so that the golden aura around his body keeps flashing. Then, he brings his cupped hands to his left side and charges a golden-yellow Kamehameha. Finally, Gohan brings his hands forward and fires the attack with the flashing light emanating from his body at the opponent, inflicting a huge amount of damage, even creating a mushroom cloud in its wake.
Gohan uses this attack in an attempt to destroy the Sealed Ball containing Majin Buu. Wanting to protect the people he cares about from Majin Buu, Gohan rejects Supreme Kai's retreating order and attacks Majin Buu's cocoon with the Electric Kamehameha. However, as the smoke clears, the cocoon appears to be unaffected by Gohan's attack. Gohan then fires several Electric Kamehamehas at the Sealed Ball, but cannot inflict any damage and instead blasts the cocoon up into the air.
Gohan tries one more time, hoping to destroy it this time, he charges it up with more power and fires it up at the falling cocoon. While the attack is blasting the cocoon, pink energy begins glowing in the core inside of the cocoon. The cocoon crashes to the ground and hatches, releasing a gaseous substance that later forms into the monster, Majin Buu.
Ultimate Gohan uses the attack during his battle against Super Buu (with Gotenks absorbed). After exchanging several blows with Super Buu, Gohan jumps in the air off of a few boulders and fires the Electric Kamehameha down at Super Buu, who counters with a Vanishing Beam. The two energy waves collide in a Beam Struggle and neither attack is able to gain the upper hand. When Gohan and Super Buu charge more power into the Electric Kamehameha and Vanishing Beam respectively, the beam struggle grows bigger until it ends with a huge explosion.