I don't think they have much of a shot at all, but Armin x Annie is my favorite ship, partially because I like each character a lot independently, and partially because I liked their interactions. They're both interested in morality intellectually but also are capable of abandoning their values to whatever degree to get things done (then later feeling remorse about it). Because of his lack of physical abilities, Armin resorts to doing some pretty manipulative things (I hope his corruption continues--it makes him a more interesting character imo). I don't even really care that much about a romance (my real Armin ship might be him and his grandfather's book). But I hope we get to see more interactions between Armin and Annie. I feel like I got to know each character a bit by better by the things they said to each other.
As for Eren x Annie, I enjoyed how they played off each other too, but it did always seem like Eren's interest was entirely platonic. (And I think I might be biased against it because I saw the anime first, and the manga plays up the non-platonic aspects more than the show does). Annie's suggestion that he learn how to talk to her girls was a bit flirty, so I think she was probably attracted to him to a degree, but at the end of the day, she seemed more to respect him than to experience "longing." Annie and especially Eren are both very mission-oriented, which makes me think they wouldn't balance each other out that well. I don't really get the support for Bert x Annie. Nothing against Bert and his crush, but since we never really got to see them interact in-scene (unless I'm overlooking something?), I have no investment. (Someone mentioned an Annie x Mikasa crack ship. I agree that could be hot in an angsty sort of way...).
I guess I don't really ship Eren with anyone. tbh I would feel bad for anyone involved with somebody that one-track-minded about titan-killing. And I'm especially against Eren-Mikasa. She's been so obsessed with him for so long that if they ever got together, the power balance would always be so skewed. That said, Eren obviously cares about Mikasa deeply, and I think her feelings for him are more than just romantic (meaning that even if he outright declared he would never have any romantic feelings for her, they still have a deep bond, and I think she could handle it). So yeah, I like their friendship/family-ness a lot! As for Jean x Mikasa, I think Jean's feelings for Mikasa fall more in crush territory than obsession, so I'm less against it than Mikasa x Eren. Jean and Mikasa'd probably have a shot at a more stable relationship (and one that could expose new sides of both characters, rather than hammering in Mikasa's protectiveness towards Eren). But I don't see that happening as long as Eren's around. Idk. I'm not particularly invested in Jean x Mikasa. Indifferent. But not against it.
Ymir x Historia is pretty impossibly sweet. Even if it turns out that Historia does not return Ymir's romantic feelings, they clearly care about each other intensely (can't wait to watch it end in tragedy).
My heart's not on the line for it, but I'm all for some Springles. Did somebody mention Hanji x Levi? I think that could be pretty funny.
Also re: Reiner's sexuality. I got the sense he was just joking about himself. Idk if this is only translation, but he says that he "didn't think I looked like the kind of guy who's interested in women." Notice he doesn't say anything about liking guys, just about not liking women--which we obviously know is false, since he digs Krista/Christa/Historia. On the other hand, that doesn't necessarily mean he's straight either. I guess I just didn't read anything into it. I could go for some Reiner X Bert tho, I guess.
But yeah, like other people have mentioned, I do like that the series plays down romantic/sexual relationships. Allows for more ambiguity and speculation--friendships often end up more interesting than love stories anyway. Who-has-a-crush-on-who plots can become crutches (The plot isn't moving along or there isn't enough tension, so just through in an easy love story).
