Gus is an old miner who was originally planned to appear in Duke Nukem Forever but was cut from the final game.
History
Pre-release (1998-2011)
From screenshots and other information released by the developers, it was long known that Gus would have had frequent contact with Duke Nukem and the Earth Defense Forces and that he likely would have been on their side. Visually, he was always shown strapped with a weapon and smiling with very few teeth. In one screenshot, he was seen happily posing with a stripper in a bar.
Duke Nukem 3D mod (2013)
In 2013, a popular mod titled Duke Nukem Forever 2013 was released for Duke Nukem 3D. Gus was included on the mod's final level, Hoover Dam, and provides Duke with a rideable donkey like he would have in the 2001 version of Duke Nukem Forever.
Leaked 2001 prototype (2022)
Gus appears in the Duke Nukem Forever 2001 prototype that was leaked in May 2022. His character has dedicated voice recordings and can be killed. However, he does not appear in a level section titled "Gus Encounter", where the player can find a rideable donkey.