As a tween, I had one of these things in the room. I believe I spent some hard-collected allowance money on it from Spencer gifts. It was an 8" globe with a potentiometer switch. (A knob allowing varied power) I spent hours marvelling at it and doing unwise experiments.
I was determined to be a mad scientist. Though, I really wasn't mad about anything.
I discovered, quite on my own in those days prior to wikipedia that if you put a magnet on the globe, ground yourself to earth and touch the magnet you would get a pretty significant little arc (relative to the transformer size driving the globe) that would burn you. It could also light a small light (incadescent.)
I thought it was magic of magnetism, I understand now to be a property of capacitive coupling. Any appropriate conductive material would provide a similar effect. (Kinda like those wireless charging mats for electronics).
Then of course, the ol' flourescent light bulb stick. The gasses in a florescent bulb passed within sufficient distance of an active plasma globe will be charged by the high frequency RF and light, quite spontaneously.
A high frequency transformer and an electrode, encased in a glass ball filled with various gasses... Different gases excite at different colors as the RF EM fields streak to find a ground.
I can't think of a practical purpose but to an 11 year old it was still the coolest thing in the world. 23 years later, a much larger one (nearly museum sized) came into my possession in a free-to-me arrangement for a paid marketing project. But, between me, you and the tax man I'd have done the marketing project for free just to satisfy that 11 year old me that still wants to build a 20 ft tall tesla coil in the backyard. (Just because.)
But, this will have to do, for now. :)