The Varon-T disruptor was a hand-held directed-energy weapon banned in the Federation due to its vicious nature: the disruptor literally tore the body apart at the molecular level from the inside out, resulting in a relatively slow and excruciating death by disintegration compared to more quick and painless means using phasers and other disruptors.
Only five were ever produced; four of them were owned by Zibalian trader Kivas Fajo and he slept with one of them under his pillow. Fajo used a Varon-T disruptor to killVarria when she and Data attempted to escape his ship. (TNG: "The Most Toys"). The fifth Varon-T disruptor was kept by the criminal Kelsey who was killed when her scout ship exploded.(TNG: "Starship Mine").
It is not clear if some of these weapons were intended to be Varon-T disruptors. Only in "Gambit, Part II" the reused prop was identified as a phaser. The type of the pistol was not identified in the other instances. TNG: "The Most Toys" was also the only episode in which this weapon was shown to produce the distinctive painful disintegration effect.