Cyber-megatron bomb
From Tardis Wiki, the free Doctor Who reference
A Cyber-megatron bomb was a cyber-bomb which the Cybermen tried to use during an invasion of Earth in the second half of the 20th century.
It was capable of destroying all life on the planet.
It wasn't used because UNIT deactivated the radio transmitter which would have delivered it from the fleet to the planet. (TV: The Invasion)
