Jan-Ken : Goku’s very first move! It’s like Rock-Paper-Scissors. If Jan-Ken-Gu is yelled, it’ll correspond to rock and the attack is a punch. Jan-Ken-Chyoki is yelled, it’ll correspond to scissors and the attack is a poke between the eyes. Jan-Ken-Pa is yelled, it’ll correspond to paper and the attack is a slap.
Goku

Jibaku: A suicidal explosion. Very powerful. #16’s was caused by a bomb.
Saibamen, Choazu, #16, Cell, Kami (only in movies)

Jidashyuu Fuku Noriyoku:Ability to repair ones self.
Metal Koola

Jigen ni Ana o Akeru: A very neat maneuver in which the user screams so loud, that a dimensional tear is created between the Room of Spirit and Time and Earth. Used so Buu and Gotenks could escape from the Room of Spirit and Time.
Super Buu and Gotenks.

Jin Rui Zetsu Mestu Kougeki : Called Special Human Genocide Attack by some. Powerful attack in which the attacker locks onto every single ki in the whole world and sends up multiple ki blasts into the air. Each blast hits a person, killing them. Only a handful survived this when it was performed.
Super Buu