In the anime Gundam Wing, the mech called Wing Gundam has a laser rifle called the "Buster Rifle". In the Megaman games, Megaman's arm cannon is called the "Mega Buster". In the Megaman X games, his arm cannon is called the "X Buster". And there's lots of other examples in anime too. It seems that "buster" is a generic term for "directed energy weapon" in Japanese entertainment media. What's up with that?