Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: D.N.Angel
Both versions of the story of Ice and Snow / Ice and Dark
The ending of episode 14, when Daisuke, alone in the darkness of his bedroom, silently pulls a veil over his painting of Risa, signifying that he's finally realized she doesn't return his feelings. Also counts as Mood Whiplash in contrast with the rest of the episode, which dealt largely with the antics of the school's new Foreign Exchange Student and super Genki Girl Mio Hio.
This troper cries every time he watches the end of this particular episode... I literally have to watch the next episode just for a change in mood.
Speaking of Mio, her whole predicament. She's a living voodoo doll who desires to be human, but in order to achieve this, she has to sacrifice Daisuke, whom she comes to genuinely care for She eventually negates the effects of the charms she gave Riku and Daisuke, sacrificing not just her chance for a human body but her doll body as well. And although for a while she appears as an annoying cockblocker for Daisuke and Riku, she actually ends upbeing greatly supportive of them in the end, telling Riku that she and Daisuke are a great couple together, in the midst of vanishing, which is a Tearjerker in universe, as both Riku and Risa are crying as it happens.