Chiyo-chan starting her second year by putting a first-year student who calls her a "little kid" in his place.
Nyamo's drunken sex ed lesson is one of the most memorable parts of the series.
The best part of all was the next morning when Chiyo asks Nyamo to explain something and the growing look of sheer terror on Nyamo's face.
To say nothing of the reaction of Tomo, Yomi, Osaka, and Kagura, who now have a new-found respect for Nyamo.
The fact that it's essentially the only thing - during three years of High School, no less - that gets Osaka's undivided attention cements it as Nyamo's Moment of Awesome.
This troper could also be persuaded to go with a couple of scenes involving Sakaki (of course). During a snowball fight, Kagura throws a snowball at Chiyo. Sakaki manages to intercept it and briefly keep it in motion before throwing it back, all without breaking it. She missed Kagura, but not by much...
Clearly, the shot was a distraction giving time for the second girl to unleash the main attack. Also, this troper now has a new favorite character. That is the definition of Cool Big Sis.
Even Kagura thought it was awesome! Usually, the reaction of someone dodging a snowball (or anything else not too dangerous) is "Nyaa! Missed me!"
I found the manga version funnier. Chiyo and Osaka are throwing snow balls at each other (and repeatedly missing). When Osaka finally lands one in Chiyo's face, Kagura asks them if she can play. Osaka quickly recruits her onto her team. By the next panel Chiyo was covered in snow bahaha.
The snowball that landed in Chiyo's face was thrown by Kagura. Which doesn't make the ensuing Curb Stomp Snowball Fight any less awesome though.
Yukari finally finding a weakness in Nyamo in the third vacation episode — and milking it for all it's worth.
This troper finds the best part about this to be everybody else's reactions to it.
Also, during the third year relay race, a boy is taunting Chiyo's lack of speed, unwittingly annoying Sakaki. She wordlessly whips her band off and ties her hair up in it, before proceeding to, having been handed the baton, regain the leaddestroy the competition.
Which unfortunately is totally ruined later, but it was still cool. Chiyo's exuberant cheering stunning even Tomo was an added bonus for this troper.
And even more awesome in that, in the manga at least, she later leaves that same boy in the dust, who can only look at her in shock.
One final touch in the manga, english translation at least: the title of the strip is "Watch And Learn." You're plenty Badass, Miss Sakaki. You just don't know it.
Also, shortly before Sakaki's part in the race, where Osaka managed to get passed by every other participant. Cue the cut to a screaming Kagura passing every single person but one, with the other members of the cast commenting on how fast she is.
Sakaki finally gets to be alone with Maya at Chiyo's house. Though she had hardly shown much emotion up to that point, she ends up literally rolling on the floor because she's so happy (watch it here, starting at 1:00). It's not a crowning moment of awesome, but rather a crowning moment of awwwwwwwwwwwwwsome.