How to open .plist files in macOS Sierra without using Xcode?
OBSOLETE (2020)
I have used Pref Setter in the past to edit .plist files graphically.
brew cask install pref-setter

Any text editor (including Text Edit) will work if the file is non-binary.  If you right click on any .plist file and click &quot;Get Info&quot;, under &quot;Open With&quot; there should be an option to change the default editor for it, which you would then change to Pref Setter. If you click on &quot;Change All&quot;, it will change it for every .plist file on your system.