I learned a really neat trick this week

shutdown /r /f /m \\computername

Reboots a computer of a given name on a network without notifying the user. Came in real handy when I was VPNed into my remote network and I was having server issues. I couldn't log onto an interactive session, but I could issue commands through the VPN. Cool huh?

UPDATE: If you look at some of the local security policies, you'll see that you have to be a member of the Administrators group by default to be able to execute this command successfully. This can be overriden by policy of course, but nonetheless, you probably cannot wreak havoc on your network with it.