Troika

From Gears of War Realm - Gears of War Wiki Strategy Guide

The Troika is a stationary gun usually used by Locust Drone Gunners. Once you clear the Drone off of it, you can freely use it by hitting the X Button while next to it. It is extermely effective, dealing out loads of damage to whatever it hits, beware though, the Troika has a limited field of fire and you are vulnerable from attack from behind while operating it.