I don't have too much fancy stuff, but over 20 years after I bought it I still love my Luminglas, currently a centerpiece on the mantel in the arcade lounge area:
With the sensitivity adjusted properly, it's reactive to the pinballs nearby (as well as everything else, ha).
But one of the coolest things I've ever found is the thing that Luminglas is sitting on: an electronic talking clock from 1981:
I'll let anyone curious look up that model number and find out how much they retailed for in 1981... it's pretty shocking. I found it in the garbage at Goodwill in 2012, cleaned it up like new and got it working. You can turn the display on/off, as well as set the interval for when the time is announced. I have the display off in the photo for a nice stealth appearance, so that the friendly female robot timekeeper catches new guests off guard 
It also prefaces each announcement with an electronic "Bing, Bong!" like a subway door closing alert, and sometimes reacts to frequency interference when I crank the stereo. It's truly awesome.
(The Luminglas also reacts and flashes every time the time is called out when the room is otherwise calm).
I once hid the clock in the ceiling in my boss' office and it drove him crazy for almost a week, not knowing where the announcement was coming from 
