New mobs that interacts with light-sources

I think a new mob that is really sensitive to light could add an interesting gameplay mechanic to Minecraft.
As long as you are in a well lit area it can't get to you.
I'd also like to see a mob at the opposite end, one that is drawn to lights to the extent that it goes out of its way and searches for light sources.
Mob behavior overall could be more dynamic and individual...currently it seems all of them just wanders around randomly until you aggro them.