Assassin is a Bukkit plugin which enhances Minecraft PVP greatly! This plugin will handle pvp in a whole new way! You remember that time you killed Bob? Bob came for you to take his revenge, he brought all his friends and annihilated you. Next time you will make sure you kill Bob anonymously, so he will not have a personal grudge against you.
The Assassin plugin tries to limit the amount of PvP by adding consequences and requirements for player kills. Now, not everyone can attack anybody at any given time. So random killing just because someone walks by will not happen that often.
Check out the Wiki for more information!
Download here: BukkitDev