Paintball guns were handheld "weapons" that fired small, non-injurious paintballs as projectiles.
Wilf used the weapon to attempt to blind a Dalek by shooting it in the eye stalk. However, the effort proved useless when the Dalek promptly vaporised the paint, clearing its vision. (TV: The Stolen Earth) Wilf later recounted this encounter to the Tenth Doctor. (TV: The End of Time)