(covers information from several alternate timelines)
The plasma torch was a Starfleet cutting tool that used a stream of plasma to cut through solid objects.
After a spike from a Romulan mine pinned Lieutenant Reed to the hull of Enterprise NX-01 in 2152, Captain Jonathan Archer carried a plasma torch with him onto the hull and was about to use it to cut through the spike when Reed stopped him, having detected detonation circuits inside the spikes. After the section of the hull they were on was deliberately detached from the rest of the ship, Archer successfully used the plasma torch to cut through the spike, releasing Reed but simultaneously arming the mine, although they managed to contain the detonation. (ENT: "Minefield")
In 2369, Commander Riker had to have treatment for a facial injury sustained during rehearsal for a play, Frame of Mind. It was postponed after another crewmember entered sickbay following the explosion of a plasma torch in his face. (TNG: "Frame of Mind")
In 2375, the USS Voyager received a distress call from the lost USS Equinox. On a search and rescue mission aboard the Equinox, Ensign Harry Kim had to use a plasma torch to remove debris from a pinned down Noah Lessing. (VOY: "Equinox")