Unlike yesterday's addition which I have strong distaste for, the evil doll is a concept I really like mainly because if done right it can be scary as Hell! Though ironically, the two most well known icons for this, Child's Play and Puppet Master I'm not a fan of... I guess that's just the example for 'not done right'. I guess I just enjoy evil dolls being much more subtle.
I'm not one to have an immediate fear of dolls, at all really, but if done in just the right light there is something unsettling about them, so I guess that's why I enjoy this type so much. It also plays off of that whole fear of something that shouldn't be intimidating is and really screws with your mind, which is where the best kind of horror comes from.
What else can I really say? This is such a cut and dry concept, but enjoyable in it's simplicity. They can range from either demonically possessed, or just inexplicably living or a cursed soul trapped inside them. Often, this is the form children will take in Purgatory, especially if they've somehow wrong someone before passing, but that's usually seen more in the form of a voodoo doll.