Right click on desktop, create new short-cut.

Type shutdown.exe -i

Click next, type in name for your short-cut e.g. shutdown computers

Click finish.

Run the short-cut you just created. Now you can browse the network for computers to shutdown/reboot etc. or just type in the IP/Name of the computer.

You can even broadcast a message, and schedule the shutdown.

Cool for sysadmins.

NOTE:  You will only be able to shut down computers that you have admin access on!