The Torrosett 51 binary heat-cannon was a type of energy weapon. It was actually one gun that could split into two guns, acting as either a double-barrelled or a single-barrelled heat gun.
Czisch's mother brought a Torrosett 51 binary heat-cannon with her to Earth, leaving it as a sort of bribe. When Pam Feerce was chosen as a host, she used one of the guns to protect herself, killing several local drug dealers and anyone else who threatened her. The other gun was kept in her house. When Torchwood Three learned of the killings, Jack Harkness was able to get one of the guns. Later, after Czisch took back control of Pam, she used the self-destruct button of the heat-cannon to kill both of them. (PROSE: The Wrong Hands)