Have you ever wondered what it would be like to be caught in a rainstorm of pigs falling from the sky? Your search is over!
With Let It Rain, you will be able to spawn massive storms of mobs over yourself or other players. You can control the creature type, the amount, the radius and the target. Raining TNT, arrows, snowballs and all blocks/items also available. LetItRain generates a config.yml which lets you edit the blacklist, the default values and the message that will be displayed when a command is called. Other fun commands also available!
For more information and download link, check the official thread here: http://dev.bukkit.org/bukkit-plugins/let-it-rain/