One of my first big projects has been to build a RepRap 3D printer.
Here you can check the wiki I made : Prusai3 Wiki
I actually made this in my kitchen, and even had some results!
Here you can check the wiki I made : My Kitchen Cloud Chamber
One day I found a little ultrasonic brume diffuser and was amazed by the power of the little device.
So I've thought it could be intersting to make a stationnary wave using that ultrasonic transducer (which works only other water).
And maybe we could even stuck little particles in the anti nods of that wave!
That little column formed by parallel lines, is actually composed of little curry grains!
I even managed to have the column horizontaly and resist to gravity!
Here you can check the wiki I made : Curry Levitation
I also had some fun building some little cymatics devices, like this Chladni plate made with an old speaker:

Or this little "visual speaker" that I exposed at MakerFaire 2015:
Even got a price for this one!
Here you can check the wiki I made : Cymatics
I also spent some time having fun with high voltage and plasma