The Focus Rifle from Halo: Reach.
The Focus Rifle is a Covenant weapon debuting in the video game Halo: Reach. It is a primarily long-range weapon, though it is quite effective at all ranges. It draws similarities to the Sentinel Beam in that it fires a consistent purple beam, rather than separate rounds. The laser will take approximately 2 seconds to kill an enemy. This weapon is designed for ranged suppression rather than the instant death, which other weapons give, and is considered a power weapon.
Its appearance and reticule is very similar to the Beam Rifle, with a 2x magnification scope