$ sudo apt install unity-tweak-tool
It can be started as Unity Tweak Tool from the Dash or
unity-tweak-tool from the shell.
I primarily use it to set the fonts in the desktop apps.
Note that when you change the Default Font, the entire desktop has to be restarted. Unity will kill all your desktop apps, logout of your session and leave you at the login screen!
Tried with: Unity Tweak Tool 0.0.6 and Ubuntu 14.04