Etsy seller Patricaia Rodriguez has created an astounding Hallowe'en prop: an animatronic door inset with an LCD that looks like a window showing a corridor beyond it. An axe-murderer stalks down the hallway, glares menacingly at you, then begins to attack the door with his axe. Each blow of the axe is synchronized with a mechanism that makes the door shake violently and causes "dents" to appear in the material, bringing the illusion to life.
You can buy the door and video together, or just the video and detailed instructions for recreating the door.
Update: from the comments, Emily Rugburn sez, "As someone who has produced fx for the haunted attraction industry, I feel compelled to tell you that this is a rip-off of another company's effect from 2 years ago - Pale Night Productions, with whom I am not affiliated."
(via Red Ferret)