Hyve Zeus
The Hyve "Zeus" is a server made for Facebook before their "Open Compute Project". As a result there's about a bajillion of these things floating around on eBay these days
Hyve Zeus units feature a Super Micro X9DRD-iF motherboard with all PCI-E slots except for one removed
They are usually equipped with some variation of low-end Intel Xeons with passively cooled heatsinks attached
The unit I (unfortunately) upgraded with two top-end Xeon 2697v2's and 128GB of DDR3 ECC memory. As a result the unit now contains two Delta R25 7K RPM fans. The resulting noise of this server renders it virtually unusable in areas with people present
It is presently part of the infrastructure of my local hackerspace. However we are likely to retire it in future