Phaser

Phasers were energy weapons which could stun or kill, depending on their power settings. (PROSE: Mindwarp)

In one occasion, the Fourth Doctor complained about always meeting people "pointing guns or phasers or blasters" during his travels across the universe. (TV: The Horns of Nimon)

In 2379, CD phasers were sold to Thordon. Specimens were found and used on Thoros Beta during an adventure of the Sixth Doctor and Peri Brown, where they were led to use them by the circumstances. Eventually, in a timeline, King Yrcanos killed Peri with a phaser as an act of mercy after her body was possessed by Kiv. (TV: Mindwarp)

While facing the threat of the Vervoids on the Hyperion III, the Sixth Doctor asked for a phaser, arousing the astonishment of his companion Melanie Bush. He secretly disarmed it, so later Doland couldn't use it against him.(TV: Terror of the Vervoids)

On the USS Enterprise a kind of phaser was in use. It proved to be ineffective against the Cybermen. (COMIC: Assimilation²)

Behind the scenes
Phasers are a classical weapon from the Star Trek franchise.