Flare gun

Barbara about to fire a flare gun at Sandy. (TV: "Desperate Measures")

Flare guns or flare pistols were signal weapons that when fired released a burning substance into the air. They were primarily used to signal for help. Barbara Wright shot and killed Sandy when she mistakenly thought he was going to attack Vicki. (TV: "Desperate Measures")

The Fourth Doctor kept a flare pistol in the TARDIS "in case [he] should get into trouble in [his] dingy", which he kept in case he should get into trouble with the TARDIS. (AUDIO: The Planet of Witches)