TR-116
From Star Trek: Theurgy Wiki
The TR-116 was a rifle developed in the 2370s decade by Starfleet Security to operate in energy dampening fields or radiogenic environments, places where a phaser would not function. The rifle used tritanium bullets that were propelled chemically. Although design schematics were drawn up and replication patterns kept, the project was abandoned in favor of regenerative phasers. (DS9 episode: "Field of Fire")
History
In the year 2373, the USS Budapest was one of five test-bed starships that had TR-116 rifles aboard. When the Budapest engaged the Borg at the Battle of Sector 001, Sam Bowers and other crewmembers used the rifles against the Borg, killing many of them and stopping them from assimilating more members of the crew. Bowers had to also use the rifle to kill his assimilated crewmates, including Captain Sh'Raazn. (DS9 novel: Lesser Evil)
In 2375, Lieutenant Chu'lak, unstable due to the loss of his friends aboard the USS Grissom, replicated a TR-116 rifle on Deep Space 9. He also made modifications to it, adding a micro-transporter and an exographic targeting sensor device. He targeted several crewmembers who had photographs openly displaying emotions in their quarters, and murdered them with the rifle before being stopped by Ezri Dax, who also used a TR-116. (DS9 episode: "Field of Fire")
The crew of the USS Enterprise used TR-116 rifles during their peacekeeping duties on Tezwa. The rifles were said to be able to shoot through walls, indicating that Chu'lak's modifications were later adopted and standardized for use in the field. They also used its sister weapon, the TR-120. (TNG - A Time to... novel: A Time to Heal)
In 2381, the crews of the USS Enterprise and Aventine used TR-116 rifles to defeat Hirogen boarders. TR-116 rifles were also used in a battle to seize control of a Borg interceptor . (ST - Destiny novel: Lost Souls)
By 2410, the TR-116 was renamed the TR-116A while a new version, the TR-116B, was fielded. With the advent of personal deflector shields, the TR-116B was designed to penetrate through them fully. (Star Trek Online)