Doraemon's reaction to losing his ears to mice. He cried so hard, the yellow paint washed off. The fact that he's permanently blue because he's in BSOD mode makes him even more of a Woobie. His voice also went hoarse because of crying so hard, which is why his voice sounds a bit odd.
Nobita's Bad Future: While not as extreme as some examples of this trope, Nobita's original future consists of him failing to pass his education, accidentally burning up his own company and crippling his family in debt for generations after his business is declared bankrupt. It affects Jaiko as well, as she lives an unsuccessful married life with him and affects her manga's career, ending up resenting Nobita for crippling them and being forced to take care of Nobita's offsprings.
Any episode/chapter with Nobita's grandma in it is either heartwarming or this.
The first time Nobita goes back in time to see his grandma, it's emotive on its own. The reason behind this? Nobita felt guilty about being too selfish with her (and just to fix his teddy bear) when he was a small kid, and now that she was long gone, he wanted her to forgive him about that, because he couldn't do so in the past. And when she finally recognizes him, the moment brought them to tears, because she knew that she didn't have too much time left to see her grandson to grow up.
There's one manga chapter with a gadget that can bring back lost items based on the user's memories. Nobita who goes overboard with it brings stuff back from his childhood and play with them, saying that he wants to drown in a nostalgia and giving up on his life. Then he finds a daruma doll and he instantly remembers one memory with her grandma. Nobita was crying on the ground after falling down on the houseyard. Nobita's grandma (who was implied to be sick that time) woke up from her futon, rolled said daruma and showed Nobita that daruma was strong because it could go back up after falling down. Nobita swore to her grandma, now lying in futon, to become strong like daruma. She then passed away right after that. The sadness after that flashback is enough to give Nobita the determination to go back to studying.
The episode where Shizuka adopts a doll and asks Doraemon to make her sentient so they can find its owner.
A similar episode where Dorami finds an abandoned doll on Christmas Eve, and when they take it to its owner, she reveals that she intentionally threw it out and asked Santa for a replacement.
The episode where Nobita accidentally called a Snow Spirit. They started as friends until the spirit became a Clingy Jealous Girl towards Nobita and forced him to play outside for hours during a snow storm. Nobita caught a very bad fever as a result. Knowing she really liked Nobita and felt bad that Nobita got sick because of her, she sacrificed herself to heal Nobita's fever and in exchange she had to vanish with the winter and spring came early instead.
The final chapter of Volume 6 of the manga, as well as the first chapter of Volume 7. Which was adapted into a half-hour long TV special in two parts.
There is one manga story where Nobita brings a past version of himself to the present to experience having a younger brother. Then, Nobita's mother sees this and starts to question whether she had another son. After the two Nobitas have an argument and the younger self runs off to his/their mother, she breaks down crying and calls herself a terrible mother, for apparently forgetting the "younger brother." As strict as she can be, it's heartbreaking to see Tamako suffer such anguish over a matter that wasn't even her fault.
Some of the fan-written endings mentioned in the main entry fit as well. Especially the infamous "happy ending", when the newly-repaired Doraemon wakes up for the first time in 35 years, and Nobita and Shizuka both switch to looking just like they did when he was last awake and glomp the confused cat. The fanbase was so convinced it was canon that they were emailing the publisher asking them to verify and/or animate it.
The song "Boku no Doraemon" can make you feel pretty bad for Doraemon.
For Doraemon's Cantonese fans, this song gets even more sad after Doraemon's Cantonese voice actor passed away on January 2, 2015.
If you are the parent of a spoiled child, Nobita might be this since he didn't care about his mom's instructions. It makes you feel bad for her since she cared about her son so much.
Lulili's sacrifice at the end of A Beautiful Girl that Nobita Loved.
"Goodbye Shizuka" can also count as this. It has Nobita deciding to cut all ties with Shizuka using whatever means necessary so that she'll have a good future, culiminating in Shizuka rescuing Nobita after he takes too many "Repellent Pills" that Doraemon gave him.
Shizuka's speech to Nobita near the end of the story can count as both this and a Heartwarming Moment, as it shows how much she cared for Nobita and how worried she was for him.
In the original Record of Nobita's Spaceblazer, where a portal to another dimension forms under a floor tile in Nobita's room. Doraemon finds a love interest there, and said portal gets destroyed at the end of the movie, severing Doraemon from ever being able to visit his love interest ever again. The movie's Award Bait tear jerker of a theme song (played as the portal vanishes) brings on the full effect.note The Mood Whiplash that follows does not make it any less tolerable.
Nobita and the Steel Troops and its remake Nobita and the New Steel Troops ~Angel Wings~ have several tearjerking moments.
The climax scene. The remakes gives more impact because of one character's screentime increase in the story. Riruru had performed a Heroic Sacrifice by rewriting Amu and Emu's programming after going back in time to 30,000 years ago, thereby rewriting Mechatopia's history. As a result, she and Pippo, beings from the present, fade due to the changes. During their final scene, they are exchanging lines. It's heartwarming to see how far they've come from hating humans; and heartbreaking, with Shizuka desperately begging for Riruru to not disappear and Nobita helplessly holding Pippo.
Riruru: Shizuka... I'm glad- Pippo: -to have met all of you. Riruru and Pippo: If I am reborn... Riruru: ...as a robot angel... Nobita: Pippo! Pippo: *happy laugh* That name... I like it very much... Riruru: ...let's be friends, okay?
Also in "Nobita and the New Steel Troops", when Riruru declares she's going to inform her commander about the gang's trickery, Nobita threatens to shoot her but can't bring himself to do it because of Pippo begging not to shoot her (as well as because of what Nobita and Pippo talked about earlier). This causes Riruru to shoot Nobita, only for Pippo to suddenly leap in front of Nobita and take the shot himself. Nobita is then left holding an injured and unconscious Pippo in his arms begging for him to wake up, but Rirurus reaction to this is more heartbreaking.
Before Mechatopia army's arrival on Earth, Nobita and Pippo spend their afternoon time together near a big lake. This scene arquably manages to be funny, heartwarming, and tearjerking.
Pippo: *angry after having been made fun of by Nobita* You take that back! Soon you're not gonna be laughing anymore! When the Steel Army comes, you'll be surprised in the blink of an eye! Even if I'm in my original body, they can't be beaten! Then you'll be crying! After that I won't show any mercy! pant Nobita: I... don't want to fight you, Pippo... Pippo: *uncontrollable cry*
In Nobita and the Kingdom of Clouds: When Doraemon and Nobita returned to Earth with a Anywhere Door (which an outraged Tamako had turned the dial with), only to find out that the Kingdom of Clouds already launched the flood several days afterwards. Once they had returned to the present time while still in the Kingdom of Clouds, Nobita then develops a dream on him finally getting a slightly lower score on his exam other than zero...while running to show the score to his parents and his teacher on a flying boat that carries them to the sunset.
The ending scene of Nobita and the Windmaster. Fuuko decides to stop a violent storm from destroying Earth by using its heated wind body at the expense of destroying itself. After the storm dies down, Nobita catches Fuuko's plush body when it falls down from the sky, crying while a montage of how they first met plays with sad music playing in the background.