Here is another cool high voltage toy that you can use for science and physics experiments. This 3D printed tesla coil gun has two knobs to adjust arc length and frequency. You can easily assemble it in under a minute. You can trigger it manually or put it in auto mode.
The body of this handheld tesla coil is 3D printed. This particular version is powered by an adapter but a battery powered version is also available. You can use this tesla coil to light up lamps and gaseous elements.