A small report. I had asked people on the subreddit, too, and received some very good ideas there. Here the list of ideas and people who proposed them:
- GUESS GAME (by beanman1103)
The person specified a size of 1x1, but I assume the size of the chamber can be adjusted depending on one's needs. Create a 1x1 dark room out of black concrete or something and have the person go inside, then place something like a diamond block (or multiple if you want) outside of the box on any side and tell the person inside to break any block. If they break a block and the diamond block is behind the block that they broke they win whatever they gambled.
- GRASS GAME (by aryski21)
Place down 3 grass blocks. Have the participant pay you 1 diamond or whatever your price is to enter. Bone meal the grass. If one flower spawns, you give them the money back. If 2 flowers spawn, give them double what they payed. And if 3 flowers spawn, give them triple. If none spawn, you keep the payment. Most of the time none will spawn, but they don’t know that.
And my personal favorite so far
- NYLIUM GAME (by SalahSaadSalah)
A coinflip type thing. By bonemealing a netherrack block in the middle of warped and crimson nylium it would have a 50/50 chance to be either one. Players can make bets on either of the colors.