Gunstick

The gunstick was the standard personal Dalek weapon. Though it was removable, it almost always occupied a space in the left socket opposite the manipulator arm. Though the Daleks sometimes replaced the manipulator arm with a more specialised tool, they almost never replaced the gunstick, except with another kind of weapon.

It was also known as an exterminator, (COMIC: The Doctor Strikes Back) beam distributor, Dalek beam gun or simply Dalek gun. (GAME: City of the Daleks)

History
A possible precursor to the gunstick was built by Davros on Skaro during the Thousand Year War. It seemed to be a larger weapon with a more devastating impact, but the sound matched that of the gunstick. (AUDIO: Corruption)

After developing the Mark III Travel Machine, Davros created the gunstick. He demonstrated this before the Scientific Elite and attempted to have the Dalek test the new device on the Fourth Doctor and Harry Sullivan, but Ronson interceded. He would later become the first Dalek victim when Davros had him exterminated. (TV: Genesis of the Daleks)

The effect of the gunstick remained standard throughout most of the history of the race from their creation onwards.

During the Last Great Time War, gunsticks were devolved into swords on the Neverwhen planet front as a result of time phasing. (AUDIO: The Neverwhen)

Gunsticks could be made into rifles that could be used by Dalek-controlled humans. (TV: Evolution of the Daleks)

Gunsticks were also used by the Daleks' humanoid Dalek puppets, emerging from their hand. (TV: Asylum of the Daleks) When the Twelfth Doctor hired Lumpy as a companion, he upgraded his non functioning gun stick, but added a bit of sonic to it, to make it a stun gun instead of a killing machine. (GAME: The Doctor and the Dalek)

The Twelfth Doctor and used a gunstick. The Doctor used it to kill Handmines, and Missy used it to kill Colony Sarff. (TV: The Magician's Apprentice, The Witch's Familiar)

Rusty forcefully removed his gunstick to prove to the Twelfth Doctor he genuinely desired to help him. (TV: Twice Upon a Time)

Physical effects
As stated above, the gunstick was an energy weapon. (TV: The Five Doctors) Although occasionally the energy was invisible, (TV: The Daleks, Death to the Daleks) the discharge beam generally appeared blue. (TV: Genesis of the Daleks, et al.) It had a "negative effect." Later models and variants exposed the skeletal structure of the victim. (TV: Remembrance of the Daleks, et al.)

Early sources of information about the Daleks described being hit by the weapon as akin to being struck by lightning, suggesting the energy involved was roughly analogous to an electric charge. Sometimes victims of the weapons appeared charred. (TV: The Daleks' Master Plan)

Rachel Jensen, examining the body of a human killed by the discharge of a Renegade Dalek's gunstick during the Shoreditch Incident, said the cause of death appeared to her to be "massive internal disruption" (paraphrased by the Seventh Doctor as "his insides were scrambled"). (TV: Remembrance of the Daleks) She later theorised that they might have been using plasma weapons. (PROSE: Remembrance of the Daleks)

The Dalek Factions present in the area at this time were using what appeared to be slightly different weapons, in that they fired bolts of energy rather than beams (and the weapons of the Imperial Daleks discharged yellow-orange bolts rather than blue). (TV: Remembrance of the Daleks)

During the massacre inside the GeoComTex Vault, the Dalek involved was able to use conductive substances such as metal and water to considerably extend the effect of its gunstick, strongly suggesting that these beams also possessed electrical properties, possibly being a form of plasma. (TV: Dalek)

While the Tenth Doctor had to regenerate when grazed by a blast from a gunstick, (TV: The Stolen Earth) the Eleventh Doctor survived a direct gunstick blast, albeit with some injury. However, this blast originated from a weakened Dalek that wasn't at full power. Due to a Time Lords' shown resistance to electricity, this supports the theory of its composition being at least partly electric. (TV: The Big Bang)

However, on a number of occasions Daleks showed a definite vulnerability to the weapons of their own kind. (TV: The Evil of the Daleks, Planet of the Daleks, The Five Doctors, Resurrection of the Daleks, Revelation of the Daleks, Remembrance of the Daleks, Evolution of the Daleks, Victory of the Daleks, Into the Dalek, The Time of the Doctor)

The Daleks of Trenzalore apparently used a massive version of the gunstick mounted onto a battlefield tank. However, it was not seen being fired because the tank with the armament in question was broken down. (TV: The Time of the Doctor)

Settings
This weapon had a non-lethal setting which paralysed the target. The Daleks said that repeated exposure to the paralysis effect would result in permanent neural damage. (TV: The Survivors) At full power, the gunstick could totally disintegrate the victim. (PROSE: Prisoner of the Daleks, The Magician's Apprentice) By the time of the Daleks' 2009 invasion of Earth, their gunsticks possessed a "maximum extermination" setting; Three gunsticks at this setting were enough to destroy a medium-sized human dwelling (TV: The Stolen Earth) or disintegrate a human being or a Time Lord. (TV: The Magician's Apprentice) Daleks of the New Dalek Paradigm could disintegrate impure Daleks with a "total obliteration" setting. (TV: Victory of the Daleks) Daleks in World War I set their weaponry to level 3 to paralyse Edward Anderson temporarily. (COMIC: The Dalek Project) During the supposed extermination of Clara Oswald and, they were both vaporised, rather than just simply killed. (TV: The Magician's Apprentice)

A Dalek could both reload and fire its gunstick by shouting "exterminate" repeatedly, as the weapons were keyed into their emotions. (TV: The Witch's Familiar)

Weaknesses
If removed from the Dalek, the gunstick could still be fired by an enemy (TV: Genesis of the Daleks, The Magician's Apprentice) or even at the Dalek itself, killing it. (TV: Evolution of the Daleks, AUDIO: Jubilee, PROSE: Engines of War)

Additionally, the beam could reflect back and destroy the user if it struck a reflective surface. (TV: The Five Doctors, TV: The Witch's Familiar, GAME: City of the Daleks)

Initially, the weapon had little or no effect on mechanical beings, though repeated fire was able to incapacitate a Mechanoid. (TV: The Chase) However, by the time of the Daleks' war with the Movellans, that flaw had been completely rectified. (TV: Destiny of the Daleks)

It was also unable to do any real damage to Sentient oil beyond briefly disfiguring it. (TV: The Pilot)

Behind the scenes
According to the non-narrative material The Dalek Pocketbook and Space Travellers Guide, the gunstick was made from a metal called Silcronian which was heat-resistant and could repel laser rays or ruby heat which the Daleks used as ammunition.