In the past few years, we have covered plenty of amazing plasma lamps here. The Luminglas flat plasma disks are specially fun as they have adjustable patterns and sound sensitivity. They were made in various colors (e.g. green, sunburst, blue) and sizes up to 20 inches.
These lamps react to your touch. They can also light up neon and other gaseous elements. In sound sensitive mode, the patterns on the lamp change as you speak or play music around it. These lamps are rare but you can still find them on eBay.