Anvilicious: Friendship is important! With the support of your comrades, you can do anything!
Broken Base: The Brave Witches season. Some fans aren't really happy for the focus of the anime to switch away from the Strike Witches themselves, where as others are fine to see the anime focus on the expansive universe of the series, or at least happy to see the anime series continue. While airing, the series got it's fair share of praise and criticism. Fans generally like how the current MC Hikari is a Contrasting Interquel Main Character from the previous MC Yoshika. However, a common criticism is the very poor use of CGI and how frequently it takes you away from the experience, the other common criticism being some of the poor writing decisions especially in episode 10 regarding Hikari & Takami.
Erica, to the point of becoming the unofficial mascot of Krautchan
Sanya's popularity is vastly disproportionate to the amount of screen-time she gets. And she was one of the first characters to receive a figurine & a dakimakura.
While The Movie cameos basically every Japanese fandom favorite they can cram in, Heidimarie in particular is given the third most significant plot driven scenes after Shizuka and Yoshika, and is basically treated as a member of the 501st (read: primary cast) at the end, in all but name.
Heidimarie herself is one from the side materials as she belonged to no Joint Fighter Wing but proved popular among fans on both sides of the pacific due to her looks, personality, combat record, and still having traces of Moe.
Perrine and Lucchini. Many of their interactions are rather amusing in terms that they're complete polar opposites, especially episode 10 of the second season, where they share tons of Ship Tease moments, including Lucchini throwing a sword to Perrine to defeat a golem, which got fans buzzing.
Mio is also shipped just as hard, if not harder, with Minna
Gertrud and Shirley are also something of a fan favorite pairing due to their interpersonal dynamics, their himegoe entries towards each other being a combination of exasperated about each others quirks and yet still highly respectful of each others skills as soldiers and officers, and finally with art by Shimada showing them both together fighting over each others food or being dressed in civilian clothing and being arm in arm with each other like a couple.
First Installment Wins: You will have the fans that say the original Strike Witches was better than Brave Witches, when comparing the two seasons, movie and OVA specials to this one season is not an accurate or fair comparison.
Growing the Beard: From episode 8 onward. This is noted in the dub commentary, when the ADR director was first assigned the show for dubbing, he wasn't that impressed at first. The strength of the characterizations and the fun way they build upon each other won him over by episode four.
Based on the events in Episode 8, Minna probably transferred her feelings for her old boyfriend (including concern for his safety) to Mio.
Eila and Sanya.... ("Doesn't it make your heart throb?"). Case in point, here is what Eila has to say about Sanya.
Eila: Sanya? ... Sanya, huh? hmm... ah, sorry. Thinking of Sanya sort of... makes my heart ache. I wonder why? ...eh? Her breasts? Sanya's!? What the hell are you looking at!? I wouldn't talk about that, idiot!
Another case was, when her dousing rods led her to Sanya's ass rather than to the Neuroi bug.
The Movie doesn't let up on the Les Yay. The most blatant example is Yoshika and Lynne; they roll around on the ground hugging at the beginning and later cuddle together in bed.
Stoic Woobie: Mio. The final episodes of Seasons 1 and 2 deal with her losing her magical power, and by extension, her ability to fight the Neuroi. Every aspect of Mio's character screams "Don't You Dare Pity Me!," but just try to watch her break down in tears in the face of losing her way of life and place in the 501st and not feel sorry for her. Fortunately, she comes to terms with it.