From Dragon Ball Encyclopedia
Future Trunks places his hands forward at a 90 degree angle and charges a blue energy sphere. He then fires the Buster Cannon multiple times from the energy sphere at his opponent, inflicting a great deal of damage.
Dragon Ball Z
Imperfect Cell Saga
Future Trunks used this attack when he and Kuririn traveled to the ruins of Doctor Gero's Laboratory. They went into Doctor Gero's Laboratory's Basement to find and destroy Cell before he could be fully developed. Future Trunks also discovered Artificial Human No. 17's Blueprints and took them in order to discover his weak point. Satisfied, Future Trunks used the Burning Storm and destroyed Doctor Gero's Super Computer and Cell's Cultivation Capsule that it maintained.