From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Masenko (魔閃光, Masenkō; Literally meaning "Demon Flash") is an energy beam wave attack used by many fighters.
The user places both of their hands above their head with the palms facing the target and one hand in front of the other with the fingers going in opposite directions. The user then thrusts their hands forward and calls out the name of the technique, firing a yellow, orange, or red wave of beam energy.
The Masenko was either taught by or taken from Piccolo Junior.
Dragon Ball Z
Gohan used a one-handed version like a rocket to propel himself out of an acidic swamp on Fake Planet Namek.
Gohan used this attack many times during the Namek Saga.
Captain Ginyu Saga
Gohan used this attack many times during the Captain Ginyu Saga.
Garlic Jr. Saga
Dragon Ball: Plan to Eradicate the Super Saiyans
Gohan used a blue Masenko along with Piccolo's Special Beam Cannon, Future Trunks Brief's Burning Attack, Vegeta's Final Flash, and Son Goku's Kamehameha to kill Hatchiyack in Dragon Ball: Plan to Eradicate the Super Saiyans.
- Bakuretsu Ranma: A combination of the Explosive Demon Wave and Masenko in which Gohan fires an energy beam with a large ball at the end. He used it against Freeza during the Frieza Saga, but the tyrant was able to repel it.
- Combined Masenko : Gohan and Future Trunks merge their separate Masenko attacks into a large, more powerful Masenko wave. They used it against Broly to no effect in Dragon Ball Z: Broly: The Legendary Super Saiyan.
- Double Masenko: In this variation, Gohan fires two Masenko blasts out of both his hands pointed at his left and right sides. He used this attack to kill Spice and Vinegar during the Garlic Jr. Saga.
- Explosive Madan (爆魔弾, Bakumadan): Adult Gohan fires a beam-like, short-ranged version of the Masenko. This move is seen in Dragon Ball Z: Budokai Tenkaichi 3 and is one of his Blast 2 attacks in his base and Super Saiyan forms.
- Gekiretsu Madan: A rapid-fired version of the Masenko used by Gohan. He used it in an enraged frenzy against Freeza after the tyrant nearly killed Kuririn. It is named in the Budokai Tenkaichi video game series as one of Kid Gohan's Blast 2 attacks. He can also use it as Teen Gohan in his base and Super Saiyan 2 form. It reappears in the Raging Blast video game series as Energy Blast Barrage.
- Super Explosive Madan (超爆魔弾, Chō-bakumadan): A more powerful version of the Explosive Madan that is used by Super Saiyan 2 Adult Gohan in Budokai Tenkaichi 3. It takes on the form of a larger and more powerful Explosive Madan with a yellow-orange flame-like appearance.
- Hyper Masenko: A more powerful one-handed version of the Masenko used by Future Gohan as a Super Saiyan. It is one of Super Saiyan Future Gohan's Super Attacks.
- Masendan: This is when Gohan puts his hands above his head for the normal Masenko, but charges it longer until it forms an energy sphere. He grabs it and throws it at his opponent, creating an incredibly large explosion. He used this attack against Freeza after barraging him with the Gekiretsu Madan during the Frieza Saga. It is seen and named in Dragon Ball Z: Burst Limit and Dragon Ball Z: Infinite World.
- Super Masenko (超魔閃光, Chō-masenkō): This is a more powerful version of the Masenko used by Gohan against Freeza, though the tyrant was unaffected by the attack. It is used by Teen Gohan in Dragon Ball Z: Budokai Tenkaichi 3 and Dragon Ball: Raging Blast. It is also one of Ultimate Gohan's Super Attacks in Raging Blast 2.
- Ultimate Masenko (最高 の 魔閃光, Saikō no Masenkō): The most powerful version of the normal Masenko. Gohan holds his hands above his head and fires a huge, golden-yellow shockwave of energy. It appears as Kid Gohan's ultimate move in Dragon Ball Z: Burst Limit and Dragon Ball Z: Infinite World.
- When the Masenko is first used by its inventor, Piccolo Daimao, he fires two energy waves one after another. The first one distracts his opponent and the second one actually hits them head on. This is fixed in later uses of the technique.
- The original Japanese audio is now widely available with the release of the Dragon Boxes in the United States. It has been discovered that despite the fact that the FUNimation dub uses the name Masenko each time Gohan gestures his hands and fires the attack, he mostly preps the attack by saying, "Kame-hame-ha" in the Japanese dub. It is difficult to tell exactly if this attack is indeed the Masenko or just another variation of the Kamehameha (as there are quite a number of them already). Gohan does say, "Masenko" randomly throughout the series, notably against Reacoom and Cell, however, there are too many instances of him calling it the Kamehameha to outright ignore this discrepancy, perhaps simply making it Gohan's personal version of his father's signature attack in the first place. It may also simply be a casual mistake on the part of Toei Animation, though it is almost impossible to tell. In Dragon Ball Kai, however, he says, "Masenko".
- The Masenko is mistakenly named Kamehameha in the Ocean Group dub.