Sonic blaster

A sonic blaster was type of weapon popular by the 51st century. They were produced at the Vilengard factory. They were seen used by Professor River Song and by Captain Jack Harkness, who brought one with him to the year 1941 during his conning days.

The Doctor switched Jack's sonic blaster with a banana at one point (DW: The Doctor Dances, Silence in the Library)

It was also sometimes referred to as a squareness gun.

Abilities
The blaster used a sonic wave projected into the form of pulsing squares of blue light which could cut through thick walls, and also had a reverse function which could replace the removed chunk of material afterwards.The only problem is that it runs on batteries (DW: The Doctor Dances)

 If Jack was capably of Time Travel why did he not simply go back to before the factories on Vilengard were destroyed and get more batteries.
 * Jack explained that the blaster used digital technology, so by implication, the blaster could encode the molecules of the destroyed materials and re-integrate them from the same source.

The Blaster has only ever been seen as a means of escape or forced entry such as when Jack uses it to destroy a door or Professor River Song uses it to blast away chunks of wall in order to escape the Vashta Nerada. It has never been used as an offensive weapon but us a tool.

Background Information
Production staff refered to this weapon as the "squareness gun". Furthermore, Steven Moffat has suggested that River's gun might be the same one Jack used, as he apparently left it in the TARDIS when he parted ways with the Doctor. (Doctor Who Confidential).