Gunstick

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

History
The effect of the gunstick remained standard throughout most of the history of the race from their creation onwards. During the Imperial-Renegade Dalek Civil War, the Imperial Daleks possibly used a different kind of weapon to the Renegade Daleks. (The Renegades appeared to still use what looked like the standard weapon.) The energy discharged was yellow-orange in colour, rather than blue, though the difference may only have been cosmetic. (DW: Remembrance of the Daleks)

Physical effects
As stated above, the gunstick was an energy weapon. (DW: The Five Doctors) The discharge beam appeared blue and had a "negative effect". On occasions this exposed the skeletal structure of the victim.

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

However, 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 Doctor as his insides were scrambled) which may suggest a different kind of weapon had been used on this occasion. (DW: Remembrance of the Daleks) She later theorised that they might be using plasma weapons. (DW: Remembrance of the Daleks (novelisation))


 * 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). (DW: 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 were also electrical. (DW: Dalek)

However, on a number of occasions Daleks showed a definite vulnerability to the weapons of their own kind. (DW: The Evil of the Daleks, Planet of the Daleks, Resurrection of the Daleks, Revelation of the Daleks, Remembrance of the Daleks, Evolution of the Daleks) As Daleks have been observed being exposed to extremely high voltage electricity and suffering only superficial damage (DW: Death to the Daleks) it therefore seems unlikely the weapon's effect is purely electrical. The fact that the beam can be reflected by a mirrored surface (see weaknesses, below) is also evidence against the purely electrical theory.

Also the beam doesn't always kill on contact as Tenth Doctor got shot and forced into a Botched regeneration. (DW: The Stolen Earth / Journey's End)

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. (DW: The Daleks)

Weaknesses
If removed from the Dalek, the gunstick could still be fired by an enemy (DW: Genesis of the Daleks) or even at the Dalek itself, resulting in the death of the Dalek.(DW: Evolution of the Daleks)


 * This was observed in one of the first Daleks that Davros created. Later Daleks may have remedied this fault, as in the latter case the Human-Daleks required a gun-like device attached to the stick to fire it.

Additionally, the beam could reflect back and destroy the user if it struck a reflective surface. (DW: The Five Doctors)