A disembodied arm that spells out messages from the ether (as long as they come through Twitter)

https://hackaday.io/project/165445-ouija-robot

Learn how to build a “jump scare” skeleton that is remotely triggered using the Blues Cellular Notecard.

A look inside a typical tungsten lamp based water-ripple projector.

This is a very generic Chinese clone style unit that lacks proper optical efficiency.
It’s designed to operate with a high output 12V 100W narrow beam lamp, but the high output lamps like that have a very short lifespan of around 50 hours. Using a lower power lamp or long-life lamp results in a much longer run time between lamp changes, but at the cost of intensity.

Nowadays these projectors tend to use LED based light sources. The ripple mechanism remains very similar between larger units like this. Sometimes with a dichroic glass colour wheel that can operate independently or in conjunction with one of the ripple disks.

The visual effect that these units produce is very subtle and soothing. Like a reflection from a pool or the sea.