Rancor Sadeye

An "unidentified Rancor weapon" may or may not exist in. The Black version of it was depicted, along with the unidentified Critical Mass weapon, on the February 3rd, 2015 update banner of SAS 4. It can also be found in the game's SWF file (pictured to the right) via a flash decompiler. The gun can be identified as a Rancor weapon by the white skull near the back of the gun, a trait of Black Rancor weapons.

As it cannot be found in the in-game "Collections" tab of SAS 4, the case may be that the weapon was just used for decorative purposes, or will be added in a later update.