Plasma balls have been around since the 80s, but these days you don't have to just wonder at them from afar.
This 80mm diameter ball is dinky enough to run off a USB port on your PC, so you can keep it on your desk, and watch as the streams of coloured lightening snake around, and react to your touch.
Alternatively use it as the finishing touch for your Mad Scientist Laboratory, no crazed meglomaniac life-force dabbler should be without one.