High frequency machine with the comb attachment fitted. I really don't like doing repairs on these bits of equipment. The sparking/arcing noise they make is scary, especially to wary electrical/electronic engineers, and associated with that noise, there's the smell of ozone emitted. There are a variety of glass gas-filled attachments that fit in it, and when operating, an arc in the gas causes it to light up.

I'll get the folk that use such things to confirm it's working okay, rather than risking touching anything other than the handle myself. Even then, moving your hand closer to the glass attachment causes the noise to become much more intense. I take that as a warning.