Neutron bomb

A neutron bomb was a nuclear weapon that, according to the First Doctor, "destroy[ed] all human tissue, but [left] the buildings and machinery intact." It was also shown to destroy the tissue of other organic matter, such as Time Lords and Thals.

On Skaro, neutron bombs were used in the neutronic war between the Dals and the Thals. (TV: The Daleks) Created thanks to the large deposits of cobalt the Daleks had discovered, these eventually caused the humanoid Daleks to mutate into the "machine Daleks". (COMIC: Genesis of Evil)

The War Lords' Security Chief decided to use a neutron bomb to destroy the humans' resistance movement, but the Second Doctor saved them by transporting them in a SIDRAT to Central control. (TV: The War Games)

In the 1970s, the Third Doctor used a neutron bomb on the Moon to destroy the Daleks' base there. (COMIC: The Disintegrator)

Steven Taylor found something he believed was "some kind of neutron bomb" inside the Monk's TARDIS. He speculated that it would be fired by the Monk's atomic cannon. (TV: "Checkmate")

Behind the scenes
In Inside a Skaro Saucer (one of the features from The Dalek World which, due to not being a story as such, is not considered valid by this Wiki), it was stated that each Dalek flying saucer contained a neutron bomb as a "suicide unit"; if the Dalek craft risked capture, it was to be activated, destroying the ship utterly and thereby erasing any chance that the enemy might be able to copy Dalek technology.