This one is going back a bit but I have obtained it for legacy support. Its a Sun V880 with 6x UltraSPARC III 750MHz processors and 12GB of RAM. Still a computer to be reckoned with [Update: Spent $50 on a new CPU/RAM board to take it to 8x CPU and 16GB RAM. eBay is great for this kind of thing]
Its as high as my desk, as large as a fridge lying on its side and sounds like a very loud aircon. [Update: When it is running under an OS at low load it throttles the fans and becomes quite quiet]
This one was going to be built with Solaris 10 on a software mirrored root using UFS but the new spin of Solaris 10 allows installation and booting off ZFS. A much more sensible choice when I have 6x 36GB disks.