A lot of the good M/K was sad, alas, because it's pretty hard to come up with a realistic happy ending, considering their circumstances. (I wish I could remember some nice fluffy M/K to cheer you up, but it's been too long since I was reading actively in that fandom.)

I agree that Legolas/Gimli is practically canon, but I would say Frodo/Sam is, too, so I can't really explain why I didn't get into those pairings.