I think every moment they spend with each other is sweet and special. The options you've provided is great but so hard to choose. But the first time when I read the part about their hands inches away from each other, my stomach ached because it was sooooooooooo cute and soooooo sweet.
I loved every moment in fact, especially the kiss, Hermione asking Ron out to Slughorn party, Ron muttering her name his sleep (AWWWWWWW) and when Ron hugs Hermione (one arms squeezes and hand squeezes). *sniffs* So cute.