Zero Player Battle Royale
I enjoy watching a good Apex Legends tournament. In the early stages of each game, I like watching the teams on a big map. You can see them all running around and reacting to each others' presence, kind of like a physics simulation.
This inspires me to make an actual battle royale simulation with the same properties. Take the same kind of battle royale rules, make a big arena, and throw in a bunch of teams. But, we program all the players to be bots that are smart enough to form interesting patterns as teams run around scavenging for kills, crash into one another other, and desperately try to survive. It would be a good exercice in programming bot behaviors. I can even make many different types of bots, then make them compete against each other, against their previous versions, or against other people's bots in a big programming competition.
Apart from being that, once I have a battle royale simulations that I can be run at will, it basically becomes a very fancy randomizer. Gather your friends and bet on different teams! Or, use it to generate a randomly ordered list. The world is your lobster.