Photonic missiles were Sontaran heavy weapons.
In 1902, the Fourth Doctor feared the Sontarans would barrage Earth with photonic missiles in response to an incursion by the Rutan Host. (TV: Horror of Fang Rock)
In 2371, at the Battle of Antares, a Sontaran Linx class cruiser destroyed a Rutan assault cruiser with a single photonic missile after the Rutan vessel lost shields. (PROSE: Lords of the Storm)