The little girl in episode 5, who runs up to Yui and Chitose while they're in costume. Her face lights up when "Rivalun" waves to her, cheering for the supposed invader of Earth as she's lead away by her mom.
S2 Ep3 - Himawari and Sakurako's moment at the end of the episode.
The flashback to little Sakurako and Himawari signing a marriage certificate in episode 10 of season 2. Capped off by this◊ moment here.
Hell, Sakurako and Himawari's relationship in general, as is demostrated in S2 Ep3 and Ep10. Despite their rivalry it's pretty clear they care a lot for each other, and Sakurako depends so much on Himawari so much that she doesn't even function without her. She becomes restless, throws tantrums and eventually just breaks down crying when Himawari isn't there for her. It's really touching to see just how close they are to each other.
Season 2, episode 8 has Yui and Chinatsu's date...of course, Rule of Funny takes hold with Chinatsu being Chinatsu.
Episode 11 in Season 2 has several moments:
After Akari tells her sister about her plans, to change the past so she didn't make such a poor first impression, her sister wonders if it's really a good thing to do. She tells Akari that if the past is changed, her memories would change too. As Akari sleeps and relives key moments from the past year, she begins to cry, and is comforted by her sister patting her head gently.
When Akari gets her last chance to change the past by preventing Ayano and Chitose from entering their club room, her sister's words echo in her mind, and she ultimately decides not to change the past after all.
Akari thinking no one would really miss her after she returns from the past. Akari didn't change the time machine to return her back to the moment she vanished (or more likely, probably didn't know how to). Consequently, she returned about a week after she went missing, to the view with all of the main characters in the club room making missing picture signs of her. Everyone of them activates Cry Cute mode upon seeing her.
Of course, none of the above actually happened; it was all a story that Kyouko wrote. Even then, it shows that if Akari really did disappear, Kyouko and the others would miss her terribly.
S2 Ep12 - Akari walks into the club room and steps on a toy snake Kyouko had been using for a prank. The look on her face and the music hurl this moment into Tear Jerker territory, before Yui and the others inform her that it's just a toy. Akari is so relieved that she didn't hurt an innocent snake, then it goes into funny territory when her purity and righteousness shine so brightly she blinds the others.
Related more to the Ohmoro-ke side manga, but in one strip, Hanako gets a cold and is stuck in bed. She mentions that Sakurako came home then immediatly went to Himawari's. While both sisters assume this is just Sakurako being heartless, cut to the end of the strip and we see that Sakurako went to Himawari's to get a recipe for porridge, after which, she made the dish for her sister.