Kellerun phaser rifle
The Kellerun phaser rifle was a type of phaser rifle employed by the Kellerun military.
It fired rapid bursts of green energy bursts. They were used by the Kellerun soldiers that boarded the T'Lani cruiser where Nydrom, Julian Bashir, Miles O'Brien, and other scientists were working to dispose of the Harvester nano-biogenic weapon.
After fending off the attack, Bashir and O'Brien each took a rifle with them to the surface of T'Lani III where they hid out and waited for Starfleet to come looking for them. (DS9: "Armageddon Game")

Kellerun phaser rifle taken from a soldier Bashir had just beaten into unconsciousness

Kellerun phaser rifle being used to destroy some dangerous knowledge

A shot from a Kellerun phaser rifle hits Nydrom
This prop began as the Hunter's weapon from "Captive Pursuit" and later became the Jem'Hadar plasma rifle used in several episodes.