A plasma-beam rifle was a weapon which the Thirteenth Doctor characterised as a "death ray".
These were capable of cleanly "slicing" boulders. When employed, the air would "sizzle" and light up like a storm, producing a distinct burning smell that would linger in small spaces.
Mark VI combat mechanicals were equipped with plasma-beam rifles, built into their right arm. The Doctor was cheerful and excited when one of these robots began firing at Team TARDIS. (PROSE: The Secret in Vault 13 [+]Loading...["The Secret in Vault 13 (novel)"])