I used to consider my workstation the "sacrificial", "sandbox", or "lab" machine, especially when I mostly ran in Windows(95) on it and only booted to Linux to experiment. (The GUI would be too resource intensive and I'd go back to Windows.)
A while back though, I set up a "test machine" in the basement so I could familiarise myself with Gentoo linux while not loosing too much productivity as I came to be more reliant on the connectivity of the now Linux-dominant workstation. The closest thing to an "essential" service that it provides is off-site access to my email (Squirrelmail on Apache), and I can usually elect not to do anything fatal to the box prior to when I might really need that access.