And now for something completely different: inspired by the strategy tabletop game Blood Bowl (the video game versions of which I've put an embarrassing number of hours into), this is Bruise Ball, a game within a game which sort of resembles American football but with a lot more hitting. Essentially, two teams of up to eight players compete on a pitch for control of a ball which they need to deliver to the opposing team's side of the pitch by any means necessary. Nothing is off limits (except for the things that are, but even they can be done so long as you slide the referee a little bribe).
This PDF contains all the base rules for how to play the game, as well as a map I made on Dungeon Painter Studio which you can use to represent the pitch. There are also optional rules for a bunch of other things, including how to build a team using NPCs and how to get a team sponsored. There are even optional traits you can give NPC players which makes controlling and buying them a much more strategic process, and even options for improving these NPCs for future matches.
This is a really fun side game you can allow your players to do in their downtime or as a one shot. I've put these rules to the test and DMed a couple of bruise ball games for my group so far, and they seemed to really enjoy it (although DMs be warned, if one of your players takes Monk, keep them away from the ball at all costs... I found this out the hard way).
The high quality PDF version of this rulebook is available on the patron dropbox (note that the PDF does not contain the map, so you'll need to save it directly from this post). If you're interested in running a game of Bruise Ball for your own groups, please do so and let me know how it goes! I would love to hear feedback about the rules and opinions on how it runs.