I have finished everyone's story except for Yosuke, but I'll get to that in a couple of hours. I think the best story is probably Labrys because she was a new character that had to be established. It was a bit of a given that she was going to have some kind of tragic story, but I didn't think it would come together as well as it did and and have such an impact. Her story and the ending to the Aigis story makes for a pretty tragic situation resolving itself on a hopeful note even though the little girl is probably dead.
In terms of canon type of information I would go with Labrys, Yu, Aigis, Naoto, Elizabeth, and Mitsuru for her overall roll and confirmation that she knows the P4 cast will be getting involved.
I think a good deal of the story lines had sad and funny moments so I couldn't really pick one there. Some funny ones that come to mind are:
-Teddy fondling Naoto.
-Aigis wanting to reveal Naoto's measurements.
-Yosuke's fear of getting ass raped by Kanji.
-Chie and her steak stuff
-Yu and his Nanako obsession in the Yosuke story.
-Kanji's story if you go down the dream route.