Most people seem to recommend "The Bitter End".  It has gotten the most
 mentions so far.  As for "giving away the story", I would expect a story
 entitled "The Bitter End" to end poorly, unless the title is a pun of some
 sort.  To hear people describe it, however, makes me believe that it ends
 in a "Romeo and Juliet"-type tragedy.  I will hazard a guess and say that
 Ranma and Akane both die, either just before or shortly after their
 marriage.
 

I, like other people, recommend it because it is (1) a real page-turner
(there's an out-of-date metaphor for you...), and (2) puts such a spin 
on your perception of the series and on Ranma's and Akane's relationship
that it is difficult to watch the show for a few weeks after you have read
this story (especially any scenes in which Akane appears).

Fortunately, it quickly becomes fairly easy to remind yourself that
Takahashi means it all to be taken as a comedy only.

The other 2 continuing stories I have *greatly* enjoyed recently are
Purple-Haired Destiny and Hearts of Ice.  

Someone has take a great deal of care to produce a guide to the
Ranma fanfics.  It is in the document  00.Ranma.Fanfic.Guide
located (along with virtually all of the Ranma fanfics) on the page
http://www.tass.org/fanfic/

--- janet