vim - and not its girlie cousin Vim -g, gvim for those who still don't get it. Emacs is ok I suppose but keep in mind the following list of tools can be done from inside of it...with LISP implementations of course.
tin - USENET still not completely useless regardless of how many outlook readers are out there. If tin isn't your style slrn is my second choice
mutt - while mail is sufficient I like it because of the vi interface
gcc - the entire compiler collection
ssh - if you can't figure out why then don't worry; you probably didn't make it past the previous suggestions.
screen - Keep your WDM and spend all your time tweaking it. If you do this you probably think MS VS is the best IDE in the world. I'll do you a favor if you can't ween yourself off of GUI's - fluxbox then ratpoison then screen.
w3m/links - You have to be able to surf. If you are new to the truly powerful ways of shell interfaces then you may want to ease into it with links -g; you do have to compile that in yourself though. (You did get this via tarz/bz2, right? Hmm, package managers - figures...)
Oh and if you must have a file browser because you don't like things such as find, grep, cd, etc:
mc although I resort to
That's about it. This should get me plenty of boos from the window zealots and the *nix wannabes.