Terrance

Terrance the turret was one of the two friendly turrets that Morgan and Katt befriended

When GLaDOS and the entirity of Aperture had been knocked offline by the detonation of a nuclear-and-EMP combination bomb cluster, a wall of turrets was deployed in Her Chambers, partially for her protection and partially as the turrets didn't know where the Light had gone.

After GLaDOS was brought back online, Terrence was later discovered in the company breakroom, decorating a Christmas tree. Morgan and Katt took turns babysitting the bullet-less turret.

Unfortunately, Terrance was still in Morgan's vault when the fire was lit by GLaDOS over the incident between the test subject and the Announcer, and the turret was destroyed in the resulting inferno.

Rest in peace, little guy.