A technique taught to Goku after he landed on Planet Yardrat following the Frieza battle. It allows the user to travel at the speed of "light" to any disclosed location as long as the user can focus on a energy signature in that location, hence the name "Transmisson".
 Users (in order of appearance)
Yardrats: A quiet and meek race of aliens, the 1st users of Instant Transmission also they taught it to Goku.
Goku: The main hero of DB/Z/GT. He use this technique more than anyone in the series and becomes quiet adept at it, he can even do it without "posing". Later on he incorporates his signature attack, the Kamahameha, with it to make the Instant Kamehameha. Sadly due to Goku using the Instant Transmission in battle and in the open a couple of enemy pick up the attack as well.
Perfect Cell: The main villain in the Cell Saga and Cell Games arc. He has Goku's cells in him so when Goku tries to sacrifice himself to destroy Cell, he just regenerates and learns the Technique. He only uses it once and that is to get back to the remaining Z-Fighters where he meets his end at the hands of Teen Gohan.
Meta Cooler: Frieza's older brother. During a battle on New Namek Goku dodges an attack using Instant Transmission, Cooler shows interest in the move and Goku explains that it's called Instant Transmission, Cooler smirks and says "I know....its one of my favorites" then the battle consists of multiple Instant Transmission mini battles.
Kid Buu: The Main Villain in the Majin Buu Saga. Kid Buu gains a lot of his abilities from fighting people and imitating them. He learns Instant Transmission by watching Goku do it when he destroys the earth. It is later recounted that he uses Instantaneous Movement (he doesn't have to hone in on energy to use it) but in fact he does when Goku and Vegeta raise their power levels to attract Buu. He also learns various attacks from Goku and Vegeta including Kamahameha and Galick Gun.