Plasma glass is a lot of fun to play around with. It looks like regular glass but lights up when close to a Tesla coil. Take the HPI Can You Imagine Plasma Mug for instance: it looks like a regular mug that holds your drink but lights up when you put it on the electronic coaster. You can also try it around a mini Tesla coil.
As you touch the mug, the glow reacts accordingly. These are hard to find but your best bet is sites like eBay.