In anime, energy weapons which fire a colored beam of light are generally called "beam guns." A similar use in American science-fiction and animation is sometimes jokingly referred to as "FX-Ray lasers" (FX is the show biz acronym for special effects). Beam guns can be poorly defined as generic energy weapons (like phasers) or very specifically and tightly defined (like the "mega particle" firing "mega beam cannons" in Gundam), which operate using the series' quintessential Minovsky particles, M-Physics being the drive behind all the superscience there.

The use of the term "beam gun" definitely predates its appearance in Mobile Suit Gundam.

Beam weapons typically take one of many forms: Beam guns, beam cannons and beam rifles depending on whether they're small or large fixed mounts (beam guns and beam cannons) or hand-held mecha weapons (beam rifles). "Beam guns" are typically energy weapons that in some way do not behave like classical lasers or particle beams - sub-c propagation rates, off-axis visibility (especially in space) and visible barrel recoil are typical non-laser-like properties found in beam guns.