I made a small minigame for Minecraft Paper servers. Each day, a new item is selected as the "Item of the Day" and players can collect it and exchange it for a reward. Server operators have the ability to set or shuffle the Item of the Day (IOTD), set the reward for the current Item of the Day, and set the default reward, which is reverted back to on date change or when the IOTD is shuffled. See the plugin in action below:
Find the source code on the GitHub repository.