So I had my perfect desktop and everything was running smooth, and then I decided to press one button on the Unity-Tweak-Tool Software and Booom, my unity-panel is gone, I can't access unity-dash and the themes don't apply correctly.
The button that messed up everything [Restore Defaults]:
My Desktop now (no Unity-Panel, Can't access Unity Dash, theme decorations to windows borders doesn't work):
I am running Ubuntu 16.04 LTS
Best Answer
I've just got the exact same problem and solved it by opening a terminal with Ctrl+Alt+T and typing these commands:
This will make unity-tweak-tool reset every setting to the default value, then reset the compiz configuration, and finally restart unity.