This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Game Grumps
"There is nothing more heartbreaking than a sad Ross."
"Ode to Jon". It has its funny moments, but it's still rather bittersweet, seeing Jon suddenly leave.
It's a depressing sight watching everyone huddled around the empty seat on the couch that Jon used to sit on, with Arin crying and rubbing the empty seat as though a close friend had died.
In-Universe: Sad Hoshi.
At least until it turns out he's a pedophile.
All of The Wind Waker: Episode 19. Essentially the entire episode revolves around Danny revealing his past where he struggled with Mono, depression, and OCD.
Danny seems genuinely sad when he realizes they've finished Kirby's Epic Yarn, especially during the scene when Prince Fluff says goodbye to Kirby.
Jon reminices about his time with Danny, and how the two used to laugh about Wolfjob together.
Jon: I miss Dan. I really do.
Many fans feel this way about the longest playthrough the Grumps ever did, Sonic the Hedgehog (2006). It was done in by Jon's departure and Left Hanging at part 108. It stops at the very end of Silver's campaign with the Grumps about to beat Iblis's final form, and they had already cleared Sonic's and Shadow's campaigns, which would have launched them into the Last Episode to beat Solaris in an epic conclusion to the game. Jon himself had said it would be an incredible finale... then left Game Grumps. Afterwards, Arin said that the playthrough was over for good, because they had gotten to a point where there wasn't much more to do near the end, and Danny felt he wasn't there for the journey and it would feel like an intrusion to pick up where Jon left off and continue only a smidgen of the game.
Arin:Like I keep saying, man. Sonic 06 is a character study on us. As people. We grow with the game, we grow as friends. Maybe we fight a couple times, but we always come back. Because we know...
Jon: [laughing] We know there's more to be had.
In Part 13 of Katamari Damacy, Dan recalls his first day of nursery school. Mixed with Heartwarming, he says how he cried after saying goodbye to his mom, and was so fussy as a result he threw blocks at kids.
Shadow of the Colossus naturally brings a few of these out, as Danny keeps saying how bad he feels about killing the Colossi.
Agro's death. Danny is "so sadmad right now."
Not helped when he reflexively whistles for Agro after defeating a Colossus... and she's not there. Danny accidentally makes himself sad.
What makes it worse is that Arin managed to trick Danny into gushing about Agro right before her death.
During the whole ending, Danny seems like he's about to start crying, and even begs Arin to cut out his shtick of pretending he doesn't know what's about to happen. He ends up declaring that he might need to take a couple weeks off before he's up to doing the next game.
Just the entire implication that Jon and Arin had a fall out adds more sadness to the fact that they seemed like such great friends, many fans even considered them brothers. To see so much dishonesty and any lack of information about what happened (which has frustrated fans alike about Jon's abrupt departure from Game Grumps) is basically this. It doesn't help that Arin barelyacknowledges Jon anymore on the show, and while understandable due to several reasons to not upset the fan base, it leaves a heart breaking feel that Arin doesn't speak about his old friend anymore.
It was actually disproven that the Miiverse post was a message about Jon, and he didn't actually say 'I don't care about him anymore', but still.
It makes worse when it's been recentlyproven by fans that the Miiverse post was in fact censored (Just not the one fans thought it was...), making the whole feel of Arin and the other Grumps (except Ross and Dan...) don't want to bother speaking about Jon anymore..
This post was apparently a violation of a non-disclosure agreement that was in place until a certain time between his departure was up. The last mention of Jon was in the very first episode of Steam Train in the beginning of the derided Hotline Miami playthrough (neither Danny or Ross impressed the viewers much because they hadn't eased into making their videos yet and didn't impress many people with their awkward gameplay), which was set to air before Jon decided to leave and unfortunately got undue flak for airing right after Jon officially left.
The hard part though is listening to Danny desperately trying to salvage the situation and put Arin back in a good mood.
Monty Oum's passing. Both Arin and Ross made incredibly touching and provocative posts to honor the spirit of one of their best friends and the hardest-working man that either of them have known.
Even worse when you consider something that happened during the Steam Train panel at Magfest 14. Ross receives a phone call coming from Monty's phone, which he ignores. It was Monty's wife trying to tell him about his coma. One could only imagine what would've happened if Ross actually answered the phone; who knows if Ross would've continued the panel if he heard the news right then and there.
In Part 2 of Metal Gear Solid V: The Phantom Pain, you can hear a twinge of sadness in Suzy's voice when she compares Hideo Kojima to Monty.
This one is tears of joy, because in part 109 of their Pokémon FireRed playthrough, they finally, FINALLY mentioned Jon BY NAME. The comments section EXPLODED.
During the "Thank You" video Danny and Ross filmed to celebrate their two years on the channel, Ross shared a story about the negative reaction to the first episodes of "Steam Train". He saw the dislike bar and the comments section, and (trying to not let it get him down) he decided forget working and spend the day at the beach with Holly. Unfortunately, he got stung by a bee on his hand and the pain caused all of his pent-up frustration he had to come out in one echoing "FUCK!!!" that shocked all the nearby swimmers and surfers. He got it patched up quickly by the lifeguards and the channel obviously sorted itself out soon after, but it's sad to hear that the negative reception to him and Danny's first appearances really DID get to them in one way or another.
Danny: You got stung by a bee, and also had your feelings stung by YouTube comments.
Ross and Dan are genuinely utterly CRUSHED when Achaka dies in King's Quest (2015). Apparently it hit them so hard that it took them thirty minutes to recompose themselves and continue recording.
In the Grump Out interview with his grandmother, Danny saying that his main regret in life is that he wished he had gotten his act together before his grandfather died, and coming close to tears because he can't see how well Danny is doing now.
Jasmine Up: I think we just saw them going through the five stages of grief.
In part 1 of Star Fox 64, Jon and Arin talk about how when they're depressed, they eat food (Jon's food being burgers, Arin's being ice cream). They mention how eating this food actually makes them more unhappy, as they lose self-control and eat too much, making them feel bad.
Part 73 of Super Mario Galaxy ends up being a very reflective, somber video as both Danny and Arin talk about how it feels like to grow older and how the current workload is taking a lot more out of them than it would when they were younger.
Danny in particular admits that the reason he's not been himself in the last couple of videos is because he's reaching 'diagnosable' levels of exhaustion with his current projects, and that the reason he's driving himself so hard is because he feels he's only got two or three albums' worth of music left in him.
Each episode gets worse and worse, as Barry and Ross become more emotionally distressed at having to kill every monster they'd previously befriended. So far, the worst is when they have to kill the Greater Dog, and they immediately end the episode afterwards because it's too much for them to take.
They finally make it to Papyrus, the first big hurdle of the Genocide run. Ross is already clearly upset, even while doing his Papyrus impression, but when it becomes clear Papyrus isn't even going to fight back, Ross leaves the room. Even Barry, who had been reveling in the Genocide run in a "I like that it makes me feel so awful" way is clearly beyond words. The episode ends with Barry giving two depressed coughs in the mic as you can hear Ross leave, slamming the door behind him.
The worst part is Ross' short yell of anguish as Papyrus is cut down and dissolves into dust.
When Ross gets back, its clear in his voice he's choking up and crying.
Dan recalling his reaction to Kurt Cobain's death in Part 60 of Super Mario Maker, and how he actually thought 27 was a fine long run at the time.
In episode 89 of Pokemon FireRed, they take Knurttt out of the Day Care, takes out one Oddish, and is immediately put back into the Day Care. The sad part is that Dan and Arin paint a scenario in which Knurttt is extremely excited to be with I never again, but is thrown away with a second thought, causing Knurttt to become absolutely heartbroken. This is played as dark humor, but can still easily be seen as a tearjerker.
The incredibly dark Alternate Character Interpretation for Lily from Petz Horse Club, that she's in an insane asylum where the staff use her for cheap labor thanks to her delusions that she's cleaning horses.
This comes from someone who went to their live show in Nyack, New York; near the tail end of the show, one of the show's staff brought in a man who had a VIP ticket, but made it late due to the Tappan Zee bridge falling apart, who gave the Grumps a heartfelt thanks for helping him stay happy even after he'd lost friends to heroin addiction.
Also from GG Live, but the last person they thanked during their whole "Special Thanks" segment was Jon, for starting the whole thing with Arin.