SGA rec - "Alterations" by Ami Ven

Author's summary: "Tag to “The Last Man”, alternate!Rodney manages to find some happiness as he makes a plan to save John."

It's McShep (though John doesn't actually make an appearance), unexpectedly touching and beautiful. I loved this one because I can actually see things going that way.

http://ami-ven.livejournal.com/302420.html