This is a simple widget which you can add to your homescreen to change the ringer mode.
You can toggle the 3 states: Ring, Vibrate, Silent (STFU).

It supports Android 2.1 to 5.1+.


Attention Lollipop users:
Google changed the behaviour of the silent mode for Android 5.0+.
The old silent mode which existed in all Android versions previous to Lollipop doesn't exist anymore.
So by Googles design the widget can only toggle the priority mode.
If you're rooted and running Xposed here is a great workaround:
True Silent Mode for Lollipop:
http://play.google.com/store/apps/details?id=com.thetonyp.truesilentmode


HOW TO ADD:
Long-press on the homescreen - Add Widget - STFU Silent Mode Widget