During the Windows 95 project, the window manager team stayed late one night and redecorated the lobby. They suspended a variety of Hallowe'en-themed objects from fishing lines: spiders, ghosts, witches, jack-o'-lanterns, that sort of thing. The fishing line went up and over pulleys, rigged so that the objects spookily rose and fell seemingly of their own volition. It was quite an impressive display.
The fishing lines were anchored to various doors in the building. Since the doors they chose were highly-trafficked, this assured a random pattern of motion for the objects suspended from the fishing line. Of course, no spooky Hallowe'en display would be complete without a spider rigged to the front door, rapidly descending upon the poor victim coming in for a meeting.