Glass cutter
From Halopedia, the Halo wiki
The Glass cutter is a deleted tool/weapon in Halo 5: Guardians. It was likely to be found in the Meridian-themed levels. It's possible this tool could have been used offensively against the Promethean invaders and would likely function as a 3rd-person weapon similar to the Chaingun turret.[1]
Gallery
A marine holding a version of it.
Sources