Water pistol
You fought her off, with a water pistol? I bloody love you!
A water pistol is an Earth made toy, which are often designed in the shape of human firearms, and are usually made of plastic. Each water pistol is required to be filled with water, and later squirted out by pulling a trigger. However, the range of which the water is squirted out is limited.
On 24th August, 79 AD, the tenth incarnation of the Doctor carried such a water pistol. He used it to hold a Pyrovile as "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 was able to see 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")