Sonic blaster

A sonic blaster, or squareness gun, was type of weapon available in the 51st century. They were produced at the Villengard factory, until it was destroyed by the Doctor.

History
Captain Jack Harkness brought a sonic blaster with him to the year 1941 during his con man days. He used it to open a door by removing the lock. After switching it with a banana, the Ninth Doctor used it to blast away part of the wall to escape the gas mask zombies. Rose, who called it a "squareness gun" because of its blast pattern, used it to create a hole in the floor. (TV: The Doctor Dances)

The Doctor destroyed one of Jack's sonic blasters with his sonic screwdriver, telling him he has seen enough weapons to last him several lifetimes and will not let the people who travel with him use them. (COMIC: Weapons of Past Destruction)

Jack had a spare blaster, which he used in New Vegas. (AUDIO: Night of the Whisper)

Jack apparently left it in the TARDIS when he was abandoned by the Doctor. The Tenth Doctor denied permission for Emily Winter to take the sonic blaster as it was reserved for "someone else". (COMIC: Tesseract)

The Eleventh Doctor kept the blaster in the TARDIS drawing room. (GAME: TARDIS, The Gunpowder Plot)

Stormcage guards had access to sonic blasters. (PROSE: A Gamble with Time)

By the time River Song used it, the handle had changed from a dark brown to an ivory colour. (TV: The Doctor Dances, Forest of the Dead) River used the blaster as a stun weapon and to manipulate access hatches into opening. (GAME: The Eternity Clock) During her expedition to the Library, she used it to aid herself and several others in escaping the Vashta Nerada, by making holes in the wall and floor. (TV: Silence in the Library/Forest of the Dead)

A policeman on a market planet was armed with a sonic blaster. (AUDIO: Death-Dealer)

Abilities
The blaster used digital technology to create a sonic wave, projected into the form of pulsing squares of blue light, which could cut through thick walls. It also had a reverse function which could replace the removed chunk of material afterwards. This was deemed a "special feature" of the blaster, and was said to use up a lot of the batteries on which it ran. (TV: The Doctor Dances)

In the hands of the Doctor and his friends, the blaster was never seen to be used as an offensive weapon, but rather as a tool for a means of escape or forced entry. However, Jack brandished the gun at those infected by the nanogenes and explained that the blaster could also function as a sonic disruptor and a sonic cannon.

When Rose used it to create a hole in a floor, it did not injure her, Jack's or the Doctor's feet in the process. (TV: The Doctor Dances)

Behind the scenes

 * The sonic blaster was designed by Matt Savage, who based it on the shape of a banana. (ImageFX magazine, October 2008, p. 62)
 * The idea of River's gun being the one Jack left in the TARDIS was suggested by Steven Moffat and was later stated in the comic story Tesseract.
 * Both the old and the new versions of the blaster are present in the Doctor Who: Legacy mobile game as separate playable characters, with no connection drawn between the two.
 * John Barrowman still has the original prop which he claims that he will be displaying in his TV room