At risk of being /that guy/, I find that emacs gives me a nice & consistent "one-stop-shop" for text-based apps instead of having to kludge together a bunch disparate terminal programs.

Also, +1 for Julia.

Just the combination of tmux and nvim with shared ctrl-hjkl between both nvim and tmux panes is so buttersmooth and no other setup has given me such an seamless interoperability between an editor and an OS. What this means: you can switch between tmux panes or nvim panes or from tmux to nvim and back always with the same shortcut. This is the most underrated killer feature.