Gladiator Games
This is a game that's really popular in Dragonspine. We usually play it when everyone still wants to play, but we don't want to set up another battlegame. Basically, you write any number of weapon combinations on scraps of paper. Variants could include shield and dagger, double flail, fireball (which remains active). Anything you can think of works. Then get the names of all the players, and put them on pieces of paper and into a hat. To begin the game, first a person pulls out the name of their opponent and then what weapon combination they will be using. The person whose name they picked also pulls a weapon combination. The two of them enter a circle, and they fight until one wins. Then the winner remains until they lose, fighting against whoever comes next.
In example: Tanath goes to the hat and gets the piece of paper with Sponge's name on it. Then he and Sponge both draw from the weapons hat. Tanath gets double flail, Sponge gets one fireball. They both step into the circle, and fight it out until Sponge wins. Tanath steps out, and Clalibus, who drew shield and dagger, steps in to fight Sponge until one of them loses.
Feel free to put any variant on this game you wish.