A palm-sized device used in interrogations ("Day of the Dove" [TOS]).

From KGT P. 55:

Klingon technology has produced two weapons used, as far as is known, only by the Klingons themselves. The tuQDoq, variously translated as "mind-sifter" or "mind-ripper," is a device that can read the contents of a subject's brain. It is considered a weapon because, at higher powers, it leaves the victim in a permanent vegetative state (though it does not seem to have this effect against those with particularly strong mental faculties, such as Vulcans). The second distinctly Klingon weapon is the QIghpej, a hand-held device that produces excruciating pain when pressed up against an adversary.