I have some ideas:
1) Hide and seek- Everyone hides and someone hunts last one to be found wins.
2) Capture the flag- There are two teams and the winning team gets a winning cash prize such as 100k each.
3)Find the button- Buttons are hid around a map and the players with the most buttons found wins.
4) Dropper- First player to reach the bottom and land in the water of the dropper wins.
5)Parkour- A parkour race first 3 players to finish gets prizes.
6)Guess the build- Each team gets something to build and then the other players have to guess the build the people with the most guesses correct wins.
7)A maze- First players to reach the end wins.
8)An obstacle course thing- Involves parkour, bridging, puzzles and other small games to reach the end.(A mix of them all)
9)Treasure hunt- Everyone is tped to a large area of cobble and there are chests hidden inside the cobble with rewards in them.
10)Survive- Everyone is spawned into an area with no armour and no pvp and mobs are spawned in and last person alive wins.
These are some ideas that I thought of. So exists already, hope you like them : ).