Well, as long as we're talking about editors, I'll recomend "EMACS" and
the varients thereof.  It used to be that the big advantage of emacs was
that it was available for everything - Tops10, tops20, unix, VMS, CPM,
MSDOS, HP150, MAC, and so on.  No having "keyboard stutter" as you moved
from system to system.  Nowdays, evolution has done away with most of
those systems, although I suppose it is still relatively rare to find
an editor that runs on both unix and windows.  The "grandpappy" GNU
EMACS comes with billions of modes and special language support.  It and
most of the popular subset implementations are user-extensible using a
lisp-like language.

The things I find most useful (aside from the programmability) include
keyboard macros and multi-file support in the form of "tags" (type a
function name and pop over to the file and location of that function),
and the automatic indentation/etc for language support...

EMACS was like THE original freeware product.  It and most of its clones
are freeware, and most are available with full source code.

BillW