Instructions
Equip an assault rifle, especially one that can fire in a three-shot burst, like the M4.
Target one of the legs of the Gekko and shoot it until it drops to one knee. While the enemy recovers, shoot the other leg until it collapses.
Run to the back of the Gekko when it collapses. The "Solid Eye" enhancement will highlight the weak point to shoot, which is on top of the "head" of the robot. Shoot at the weak spot.