Shutter
Simplest desktop multiplatform app for scheduled Shutting down.
...I present you the Shutter App. This app has the simplest user interface and all the UI elements does what it is meant for in this app. This app can perform instant shutdown, instant logoff, instant Restart and timed Shutdown. For using timed shutdown all you have to do is to enter the time in seconds after which you want to shut your computer.
Shutter is a very very light-weight, simplest and platform independent app, so it works flawlessly on Windows, Linux and Mac Operating Systems.