Photonic cannon
The photonic cannon was an imaginary type of directed energy cannon, a weapon of mass destruction, created by The Doctor on board the , after he added daydreaming subroutines to his program. This weapon was supposedly impervious to all conventional sensors, and had enough power to destroy a Borg sphere with a single volley of two lightning-like energy beams. 

The Doctor used the concept of a photonic cannon as a bluff to prevent an attack on Voyager by a Hierarchy starship, with the help of , who convinced his superior officer about the weapon's awesome power. ()

See also
Corbomite

de:Photonische Kanone
es:Cañón fotónico
Fictional weapons