Sukinasaki Saki suddenly stripping in the middle of a concert.
The next chapter, Kikaijima, while onstage, in a swimsuit, shouts out her feelings to Medaka, starting with:
Kikaijima: "Medaka is STUPID!" (thereby voicing out what the student population felt about Medaka generally)
Tsurubami's blasť reaction to getting beaten up by Medaka.
Chapter 146 has a truly hilarious revelation. All throughout the series, Zenkichi has wanted to confess his love to Medaka. He ultimately decides against doing so when he has the opportunity because he thinks it'd be selfish to deny Medaka all the wonders of life by immediately tying her down to him after setting her free of her messaiah complex. While Chapter 140 ends with Medaka kissing him and saying she's fallen for him, it was always possible this was just Medaka being Medaka and it had no meaning at all. Then comes chapter 146 and we learn she actually asked him to marry her when they first met. At age 2. Zenkichi, being just a little kid, says no, crushing her. Naturally that was long ago, so Zenkichi probably forgot, but Medaka never did. It's not that she hasn't been able to fall in love that's kept her from having relationships in the past. It's that she's always loved Zenkichi, and admits she felt lucky he let her be his friend, unaware he feels it's the other way around. This whole romantic subplot could've been resolved long ago if they could just talk about it.
Chapter 151: Zenkichi's epic rejection. Also counts as an awesome moment.
[Leave that stuff to the preschoolers!]
Ajimu leaves a Video Will of sorts for Kumagawa in the form of a fully physical but pre-recorded her. She correctly guesses at what point he would try to peek up her skirt and kicked him in the face.
Ajimu: I can't see you but I can more or less predict your actions, so I'll just throw a kick here for good measure. If it connects; hooray for me.
In the very last arc, Medaka leaves the academy out of her own free will. The characters organize a grand sendoff including just about every named character in the series. Zenkichi resolves to look forward as the Student Council President and at the next Entrance Ceremony Medaka returns as the new Academy Chairman. Zenkichi face-faults and everyone is shocked except for Kujira. A small text box points to her saying "she knew".