Happily Married by Kirinin
Ranma wakes one day to find that a couple of things are different. Nothing major, just a new life complete with child, dojo to run, and, most importantly, a spouse. Problem is, the last thing Ranma recalls is being sixteen... COMPLETE! Now in Italian too.
The Promise by TheonLee
Friendship lasts a long time. One will do anything to make up for what he's done. Soon, both find something more between them. Completed.
A Tale of Transformation and Tragedy by Rowan Seven
A magic fountain makes one of Nodoka's desires come true in a way she neither desired nor expected. Ranko x Ryouga, with a twist.
This one sort of counts except for the end.
Dew on the Grass - Richard E
Akane causes Ranma to hit his head making him think he's female, this lasts longer than anyone expects. Ryoga attacks the newly dubbed Ranko but when he finds out who she is he feels guilty. Ranko, being sweet and kind works with him to alleviate his guilt and they slowly fall in love. Unfortunately when she has a nekoken attack, it shunts Ranma's personality back into possession and Ryoga loses his Ranko.
Hope this helps. The first three fics have a slightly more descriptive summary on my
Rankofics webpage