EreAnnie

Ereannie is the het ship between Eren Jaeger and Annie Leonhart from the Attack on Titan fandom.

Canon
Eren and Annie have shared a mutual respect ever since their trainee days. As sparring partners, Eren sees past Annie's cold exterior and listens to her ideas as well as reiterates what she says. Their close bond is the reason why Eren initially struggles to accept the reality that Annie is the female titan (which provokes a jealous Mikasa to question whether Eren has "special feelings" for Annie). After their destructive titan brawl, Eren freezes at the sight of Annie's crying face and this hesitation is what gives Annie the opportunity to crystallise herself.

Fanon
Post time-skip, Eren and Annie are arguably just as villainous as each other. Both have abandoned their humanity...for the sake of humanity. If they meet again it is possible they will have a deeper understanding of each other due to their shared experience, and this may lead to a romantic relationship between them over time.

Fandom
AO3