The most gut wrenching part of the books for me was Dobbie's death and his burial but somehow the films fumbled that.
Longbottom is second only to Harry as a fighter and as likely to be "the chosen one" as Harry. His badassery and the fact that they were both the chosen one also gets dropped in the films.
The real trigger that made Hermione jump Ron's bones was S.P.E.W and the fact that Ron showed that he had quietly always listened and supported Hermione. He always had her back and never looked or asked for anything in return. In the films it was "Whoa, scary snake! Let's make out."
I read the books once, when released, and these still stood out to me.
Well, Neville was not the chosen one, since Voldemort specifically didn't choose him. But he could have, which is an important aspect absent from the films.