Voted for
- Apple MacOS/Mac OSX
Apple's MacOS is my primary and favorite OS without a doubt! I have used it for nearly a decade now and it still is an OS close to my heart.
If I had to choose a secondary favorite OS, it would be Linux, specifically a Debian/Ubuntu distro or flavor. Linux, also being built on a UNIX(-like) system means I am quite comfortable working between Mac and Linux without issue.
There is one OS I unanimously hate using, and that is Windows, especially Windows 10. It is a horrible OS and I have nothing good to say about it. I would never voluntarily use it if I could.