This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Gunparade March
Gunparade March had a few heartbreaking moments, but there is this moment when two characters talked about how Nonomi is a genetically created human being that won't grow up from being a seven-year-old, both in body AND mind, and that she is used as a weapon against the monsters that are bent to utterly destroy humanity, because she and other kids like her are the only thing that works against them. While showing Nonomi acting all happy. This troper, who disliked her up to that point, cried so much she had to stop the DVD for a few hours before going back where she left.