Book: Vex Arsenal.
The Vex Line Rifle fires high-velocity Solar particle jets. Deployed on the Hobgoblin chassis, the Line Rifle serves as a sniper weapon, pinning down targets or delivering the killing blow.
Like the Slap Rifle, the Line Rifle is a terminal weapon, although its source is much more energetic. Some believe the weapon pulls material from the accretion disk of a galactic singularity. This would imply the Vex are near - or have already achieved - access to a terrifying range of civilization-killing weapons. Others consider this unlikely, and propose that the Line Rifle simply draws from a central Vex power supply.