Water pistol

A water pistol was an Earth made toy. They were often designed in the shape of human firearms, and were usually made of plastic. Each water pistol required water in the barrel, which was later squirted out by pulling a trigger. However, the range of which the water was squirted out was limited.

The Tenth Doctor found a water pistol in his pockets while looking for his sonic screwdriver. (DWAM: The Germ War)

Later, while visiting Pompeii on 24th August 79 AD, the Doctor used a water pistol to hold a Pyrovile at "gunpoint" to gather information from it. Knowing actual guns weren't invented at that period, he was able to get away with the fact that the Pyrovile believed it was a dangerous weapon, until a member of the Sibylline Sisterhood looked into his mind and called his bluff. However, squirting the toy at a Pyrovile-controlled High Priestess still caused it to feel pain, since water was the Pyrovile's weakness. He later used it again on an adult Pyrovile inside Vesuvius, causing a similar effect. (DW: The Fires of Pompeii)

The Doctor later used a water pistol to find the rear entrance to the Temple of Kol-Ne-Wah. (IDW: Final Sacrifice)

In 2008, Royal Albert Hall was briefly invaded by a Graske armed with a water pistol he had stolen from the Doctor. (DW: Music of the Spheres)

Behind the scenes

 * In the 1960s, Dr. Who's Anti-Dalek Fluid Neutraliser was released; it was a simple water pistol.