ClientMinigames adds a collection of mini games to Minecraft that you can play directly inside the game whenever you want to take a break from your usual gameplay or just have some fun.
The mod currently includes 6 mini games:
Every mini game includes its own leaderboard.
Compete with other players, improve your scores, and try to reach the top of the rankings.
Unfortunately, I can't guarantee that all results are legit because any minecraft mod is easy to hack, but it's still better than just turning off the leaderboards.
ClientMinigames provides a convenient API for developers that allows you to create and add your own mini games.