For the heck of it, what's the fastest way to kill a server, other than just pulling the plug?
Kill as in a(n) (un)safe shutdown, you could theoretically reboot it and have it survive the incident.
Edit: Tangentially related to serverfault.com, my apologies. IMHO, the question is related in that these are possible things users could be attempting, as well as in the case of adverse conditions there might be reasons server admins want to take down multiple boxes lest undefined "damage" might occur.
Edit2: opened to community wiki.