Oculus

Oculus are fast-moving devices used by the Collectors to protect the Collector base. It is unknown if they are actual fighters piloted by Collectors, or some form of remotely-controlled drone.

Oculi possess powerful beam weapons, similar to other Collector weaponry, and can invade an enemy ship by cutting into its hull after jettisoning part of its armor.

The Normandy SR-2 was attacked by several Oculi when attempting to reach the Collector base. The Oculi were apparently left on guard in the local debris field and only activated as the Normandy approached. While most of the Oculi were destroyed by the Normandy's weapons or by accidentally flying into debris, one was able to invade the ship. It was eventually destroyed by Commander Shepard.

It is likely that the Collectors gained the Oculus technology from the Reapers.

A squad member (Jack, Jacob, Legion, or Thane) may be killed by an Oculus particle beam unless Shepard upgrades the Normandy SR-2 with Heavy Ship Armor.

Trivia

 * 'Oculus' is Latin for eye.