Dalek smoke

Dalek smoke was, according to some sources, what Daleks used to exterminate their enemies. The smoke would emerge from their gunstick. (TV: Dr. Who and the Daleks, Daleks' Invasion Earth 2150 A.D., et al.) The smoke was once described as a radioactive gas that would "[disintegrate] nervous cells upon mere contact." (COMIC: Daleks, invasión a la Tierra año 2150)

Many other sources suggested that gunsticks would instead shoot energy blasts (TV: Dalek, et. al) which would scramble the victim's insides. (TV: Remembrance of the Daleks) On one occasion, Dalek casings built on Earth used riot gas that resembled gun smoke. (TV: Revolution of the Daleks)

Behind the scenes

 * The Daleks in Dr. Who and the Daleks were originally supposed to have flamethrowers as their main weapons, replacing the futuristic gunsticks of their televised counterparts. This was eventually replaced with gas weapons, but a flame-spouting gunstick is still prominently visible on the Black Dalek in one of the early posters for the film.