Share your own game rules you have made up that are not the way the game was originally meant to be played.
One that I remember is in “Monster Jam” for the Nintendo Wii, there is no free roam but you can play a “destruction mode” that has a time limit but works good enough. There is a map where you can go up on a roof and the goal is to push the other ones down being the last one standing when the time hits 0. That’s it. It was inspired by an flash game with the title “one must fall” I believe.
We played this a lot. Its funny how you only need a “interesting” physics engine for a game to be fun.
From the title I was thinking of, like, Grognak’s Adventure inside of Fallout 4.
But from the body text… Yeah, I don’t really do that. I am usually pretty annoyed by how many servers for games I want to play aren’t actually playing the game itself, but their own game inside the game and making up their own rules. Which is totally fine, but it should advertise it somehow or not even be public as many of these groups just kick randos out anyway.
I do like a lot of mods that were inspired by these games within games tho. ARMA Life only exists because people were already trying to play the normal game that way, and with the mod the rules can be more easily enforced through scripts instead of requiring hands-on management from an admin.