Bukkit

There are many potion effects in Minecraft and they do not always become used as well as they could be used. When in game, and health is low (say 2 hearts left), a potion effect defined in the config would take effect such as the blindness effect that creates a black fog around the player. Perhaps zombies could be configured so that they give off a potion effect when they "attack you." For example, when a zombie hits you, the potion effect 'Nausea' occurs for one second (ability to change time of effect in config) (Nausea creates the wobble effect we get when entering the Nether).

Full list of Minecraft Potion Effects: http://www.minecraftwiki.net/wiki/Potion_effects

That's an original idea, I like that :)