I hosted a Minecraft server for some friends and wanted to add some more fun mechanics, so I made some plugins using the Bukkit API.
Keypads
Minecraft plugin to place keypads next to iron doors. The player can interact with the entity and will prompt them with a inventory GUI.
https://github.com/MrAuro/keypads-plugin

Oneway
Sends a block change event to a user if they are in a certain zone, causing the face of a wall to be see through only for that person.
https://github.com/MrAuro/mc-oneway

Cards
Allows players with permission to give themselves a deck of cards that lets them draw a random card with right-click.
https://github.com/MrAuro/mc-cards

Nospawn
Prevents entities from spawning in a certain area which can be toggleable by players with permission. Made because I didn’t need all of the advanced features of WorldGuard.
https://github.com/MrAuro/mc-nospawn