Here are couple:

The scene between Blair and her mother is really touching and serious

The scene between Jo and the journalist teacher ranks as both a very serious take on a touchy subject that the teacher was caught

The suicide of Cynthia is both emotional and serious.

Which do you rank among your FOL scenes?

there are soooooooooooooooo many, here's what comes ot my mind...

between mrs. g and natalie over the death of her father
between mrs. g and blair (and kind of jo) over her attitude lately - working it out
between natalie and tootie over whether she should sleep with jeff or not - my boyfriends back
between mrs. g and tootie when her brother drove them back drunk - let's party

lots between the girls and mrs. g

The scene between Jo and Mrs. Garrett in the cafe towards the end "Teachers' Pet" as well as the scene in the hospital between Jo and Blair in "Less Than Perfect" are both very moving.

*the scene between jo and natalie when natalie lost her virginity to snake and was upset.
*the scene when natalie was attacked and almost raped.
*the scene between jo and blair when blair got into a car accident and was in the hospital.
There's so many!!!