Mine is nothing unique, but it’s still pretty damn cool - even just to watch. We have two Sun StorageTek SL8500 Tape Libraries. I could sit there all day and watch those little robots zip around their tracks, pluck tapes from one place, and zip them over to another, over and over and over. Here’s a YouTube video I found that shows it in action. These things can scale to 70,000 slots (about 56 petabytes*). Our two SL8500s are connected in the back so that they can pass tapes between them, which is pretty cool, I think. The base price for a minimally configured SL8500 is $195,000.
*That video shows them using 9840 tapes, which are kind of old and lacking in space, but it’s capable of using LTO IV Ultrium tapes (800GB native/1600GB compressed). Ours are filled with LTO IIIs (400GB/800GB).