Recently there was a discussion on www.slashdot.net about uses for empty hard drive bays which reminded me of a particularly disturbed iguana I used to have years ago.
This thing was a "Gift" from someone else. Some gift I tell you. It would scratch around at night, keeping me awake so I thought well I'll let it out. What a mistake that was! It decided my bed was his territory not mine and I found out when I put my head down on my pillow and well I won't go into any further details. I'll just leave it to your imagination.
I had this home built system with four huge hard drives connected to my computer. They were too big to fit inside so I left part of the back cover off and just connected them externally. The first external hard drives in existence that I knew of in the late 1980's. It was a system only a geek could love being proud of a system with about 100mb if data storage which in those days was huge!
Well, I had this huge three foot iguana I inherited and I made a roost for it by the computer. That was a mistake! It was calm much of the time but would suddenly and without any apparent reason dart off like a rabbit to hide inside what qualified as the nearest hole which this time ended up being the empty drive bays. Suddenly this huge monster is frantically ripping a hole through wires, chips and other innards like some crazed reverse alien being trying to get in instead of out.
Next day I took it to the pet store and they found a better but less shocking home for it.
So I guess this might qualify as the most unique but impractical use of empty hard drive bays.