Bukkit

Allows players to bind item such that they are destroyed upon death and drop.

Allows worlds to be "space worlds" in which being without your space suit can prove deadly.

Cards for a quick summary about one's roleplay persona.

Allows for the use of /tpa like commands without needing permissions.

Allows for users to fire arrows at one another on command.

Tag a player and they cannot enter the spawn for 20 seconds!