By the fall of 2002 I had been playing Day of Defeat for around three years. That's when I tripped across a server named Ratz on Toast. It ran small fast custom maps all from the same map maker who's name escapes me.
Long and short of it is this. There were two clan like groups of players that called this free server home. I rented three for servers and formed both groups into a clan which eventually grew to include three league teams in four leagues.
Many other members were heavily involved in community created content in the form of every thing from custom models, maps, server plugins, and in the case of Zor and Havoc, the code for DoD United Admins.
United Admins started as a collaboration of a dozen or so admins from the most popular public servers. The plugin banned you from all participating servers if you were banned on any server for cheating. Before too long it caught on and more admins joined up.
The code was developed by the community and eventually Valve used it as the "bones" of VAC.
So now to the moment you've all been anxiously waiting for, the origin of the dancing Hitler stick and GIF.
Remember when I said there were two clan like groups on the Rats on Toast server?. Well one of the two called themselves WwW or World War Warriors and was "led" by a kid who went by. Grimm.
Grimm was smart old. At just 17 he was doing three hours a day of college court work in mathematics at some private academy in NYC.
Anyhow in Half Life/Counter Strike/Day of Defeat you could "spray" a decal on the map. This GIF was made by Grimm as the first step of creating it as a custom in game decal to spray on the map.
That was over 20 years ago and I still found a copy of it by searching "dancing Hitler GIF stick an".
Crazy...