Bright Weapons is the term used by Obesk to describe weapons used by the Bright Cousins, specifically firearms. They fire "dead metal" (normally bullets) as opposed to the Corru utilized in Obesk equipment. In the Collapse memory, Disablers can be considered an analog to these weapons.
In Kazki's room, a prominent selection of bright weaponry is displayed. BSTRD also makes use of what appears to be an M4A1 from the contents of the Scary black box.
Modified versions of bright weapons are used for the Symbiotic Rifle augment in Recollection: Collapse, notably draining the HP of their user upon firing. This is in part that it utilizes the corru of its host to create projectiles.