Arch Linux with Xmonad is my primary OS. My favorite shell is zsh.
I used to mainly use Debian-based OSes, but now I use Arch Linux for basically everything.
My preferred desktop environment is Xmonad, despite how much I loved KDE Plasma 5. It was really slick, faster than Unity, and has a neat function to integrate with mobile devices. But Xmonad is just so much more powerful. Every once in awhile I need to switch back to a normal window manager, so I use KDE, but that's basically only for certain fullscreen games.