GNU Emacs
GNU Emacs is my editor of choice when I'm hacking on entire software projects like GIMP (but for merely changing server config files I usually prefer the more lightweight vim).
GNU Emacs along with a handful of external libraries and an elaborate .emacs (these to be precise) makes up a rather nice IDE on Linux. I do think however that GNU Emacs suffers a bit from its terminal text-only heritage. Here are some things I'd like to see in Emacs and that I hope to one day get time to write some patches for:
- Inline completion candidates: Instead of showing completions in a *Completions* buffer, show them in a popup-listpopup-list right after the word to be completed.
Ok that was the only thing that came to my mind right now...