There hasn't been a lot of Half-Life 2: Episode Three or Half-Life 3 content from the enormous 12 terabyte Steam leak, aside from a few strings buried in the files, but there was a nugget of gold in the Portal 2 beta. And no, I'm not talking about hot GLaDOS this time.
It featured the unidentified weapon first shown in the Half-Life 2: 20th Anniversary Documentary as a placeholder model, likely standing in for the paint gun. So, it's still unclear what exactly it does, other than use the same ammo as the Tau Cannon and Gluon Gun from the first Half-Life, but this leak finally gave the community an official model to work with.
So, in typical Half-Life fashion, it was immediately modded into Half-Life 2 as a skin for the Gravity Gun. There have been mods in the past that tried to replicate the look of the unidentified weapon based solely on the documentary footage, but this is a real, tangible, Episode Three model designed by Valve that is now accessible through mods in the game. That's a pretty big deal. With some tinkering, it could easily leap from the realm of skin...
