I am obsessed with autocompletion in shell mode. Running a shell in shell-mode instead of a terminal emulator has so many advantages. You can treat the whole buffer just like a normal Emacs buffer. You can copy and paste and edit the line normally. You can hook it into native Emacs functionality. You can even display images! However there is one big disadvantage. You loose access to the state the shell.
I see many threads on Reddit and blog posts about using email inside Emacs. I mean, I already have org-mode which organizing my whole digital life. But then all my work email is provided through outlook, which does not allow me to fetch email with anything other then their proprietary software. Microsoft outlooked was designed to be used by people writing marketing emails, not people talking about code. There is no way to