From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Vegeta holds out his hand with his index finger pointing outward and his thumb pointing up like a child pretending to have a gun. He then utters, "Bang!" and a red, lightning fast bullet emits from his finger and strikes his opponent with deadly force.
Dragon Ball Z
The Bang Beam was a favorite move of Vegeta during the Namek Saga. He used the attack to murder a Namekian villager while interrogating his village for the Namek Dragon Balls. Vegeta also fired a full-palmed version in his battle against Zarbon.
Final Form Freeza was also shown to use his own version of the Bang Beam during the Frieza Saga. He used the attack to kill Dende so that the Z Warriors would not have any more chances of being healed by him. He also used it in an attempt to kill Son Goku, after getting hit by the Large Genki Dama, but Piccolo got in the way and was hit instead.