Defabricator
The defabricator was a device from the year 200,100. It was previously used by the Trin-E and Zu-Zana robots on What Not to Wear. Its original use was to "defabricate" clothing by making it literally disappear. Captain Jack Harkness was able to upgrade the device into a powerful weapon, by tweaking the system, after he destroyed the robots, who tried to kill him. (TV: Bad Wolf) The weapon fired a bluish beam of energy that was capable of piercing Dalekanium armour, and hence could destroy a Dalek. When a Dalek inadvertently materialised on board the TARDIS, Jack used the weapon to kill it, but this resulted in depleting the power source. (TV: The Parting of the Ways)
Jack had somehow managed to have brought this weapon along with him and used the weapon again when the Earth was stolen by the Daleks. Apparently this time he had replaced the power source with a better one as he was able to use it at least twice; killing a Dalek and the Supreme Dalek. (TV: The Stolen Earth / Journey's End)
