The Compact Laser Deluxe was a powerful laser weapon that was extremely small though still quite noticeably sizable.
Its compact dimensions were proven as Captain Jack Harkness managed to store it away somewhere "you really don't wanna know", presumably in his backside, in case of emergencies. Its only known carrier was Jack Harkness and it was used by him to destroy both the robots, Trin-e and Zu-Zana. (DW: Bad Wolf)