Unwanted supernatural guests (as opposed to the wanted kind) on film tend to come in two varieties, (1) a ghost or spirit haunting a particular place or abode, usually, but not always isolated, due to unfinished business with the living or a refusal to move on to the afterlife, whatever it may bring, and (2) a demon or devil sent to cause mischief, torment the living, or otherwise cause havoc, usually, but not always, through bodily possession. Together, these sub-genres exploit our fears and anxieties, of mortality, of bodily decay, of losing our selves, of the past injustices or crimes, of repressed and suppressed desires, returning to disrupt normal, everyday lives. That and we, meaning almost everyone, likes (even loves) to be scared.
So without further delay, "Cinematical Seven: Unwanted Supernatural Guests' (in alpha order, not order of preference):
1. 'Dark Water'
Returning to the well (so to speak) for a second time, Hideo Nakata's 2002 adaptation of 'Ringu' author Koji Suzuki's novella, set inside a dilapidated, semi-abandoned, water-logged apartment building, builds slowly toward a devastating, wrenching climax for its single-mother protagonist and her young daughter. 'Dark Water's' ghost, a yellow-raincoat wearing girl, may not be as malevolent as its 'Ringu' counterpart, but it's driven by an insatiable need for maternal comfort. Post-'Dark Water,' no ceiling stain looked the same.