If you've been using Windows 8 for some time now, you probably know these two things: One, you can add programs to the Start Screen for quicker access, a list of frequently used favorites in tile format. Two, the shutdown command isn't as accessible as it was on older Windows versions.
Here's something you probably don't know: the shutdown command is actually its own program. This means you can create a shortcut to it, and add said shortcut to the Start Screen for more straightforward access.
Go to the desktop, right-click on an empty area and select New > Shortcut. Under "Type the location of the item:" enter "shutdown.exe -s -t 00". It's up to you what to name this shortcut. Afterwards move the new shortcut to X:/ProgramData/Microsoft/Windows/Start Menu/Programs (where X is the drive where Windows 8 is installed). Go back to the Start Screen and you'll see your Shutdown shortcut as a new tile, providing much more accessibility.