Jim proposes to Pam at the rest stop in the rain. "I just couldn't wait any more."
Jim's reaction to Pam's pregnancy in Company Picnic.
Pretty much every single moment Jim and Pam have with their newborn daughter, Cecilia, in "The Delivery." At least their own newborn daughter.
It's not really presented as heartwarming, but in "Customer Survey" Jim and Pam miss each other enough to spend eight hours a day on the phone together.
"I'm coming back the wrong way."
"You bought me a house!"
Most of Jim's wedding speech, at least up until he accidentally reveals Pam's pregnancy.
The end of "Niagara," with the shot of Pam and Jim after their secret wedding - Pam resting her head on Jim's shoulder just like in their Sleep Cute in "Diversity Day." Not a bad day, indeed.
Pam relaying to Jim that what he said to her father caused her parents' divorce (he told her father how much he loved Pam, which caused him to realize he had never felt that way about Pam's mom). Doesn't sound heartwarming. It is.
Pam: Every kid grows up thinking their parents are soul mates. Our kids are going to be right.
Left side of the page: Pam, Cece, new baby. Right side: Everything else.
Michael shows up at Pam's art show and raves about the quality of her artwork, creating perhaps the show's most touching moment.
As Dwight leaves the building after he quits in Season Three, he meets Jim and hugs him without saying anything, showing that despite everything they do to each other, he actually cares for him.
Michael rehiring Dwight in Season Three.
Jim comforting Andy with an acapella rendition of "The Lion Sleeps Tonight".
Jim comforting Dwight after his breakup with Angela.
Jim: ...it is something that I wouldn't wish on my worst enemy. And that includes you.
Jim then silently leaves, just before Dwight (with his face against the wall) turns to give Jim a hug or a pat on the back, and finds the space empty, leaving him to wonder if Jim was EVER THERE AT ALL.
In a similar fashion, Dwight channels his efforts to win Angela back into selling more paper in a day than the newly-launched Dunder-Mifflin website. His loud antics throughout the day are enough that Jim and Pam retaliate with a prank that fools Dwight into believing the website has achieved sentience and is instant messaging him. Dwight achieves his goal by the end of the day, but his glee is immediately replaced by depression once Angela claims to be unimpressed. Pam sees this, and has the "website" send Dwight the message "You beat me. You are the superior being." Dwight's eyes water.
Subverted by Dwight. When Pam helps Jim and Karen get back together in season 3, it makes her break down in tears. Dwight starts to comfort her, but then blows the moment in typical Dwight fashion.
Dwight: "You must be PMSing pretty bad, huh?"
Dwight's immediate reaction to seeing Pam crying is to ask her who he has to attack, making it a straight example as well.
Andy gets his in this troper's opinion when he fakes sick at work to make his date with a sick Erin at her house, bringing what appears to be soup.
Michael coming to Pam's art show, and telling her he's proud of her.
Though Michael and Jan have an entirely unsympathetic relationship from start to finish, this troper found the moment they shared on the train to be quite touching, especially as it's the one and only time Jan actually makes any kind of effort what-so-ever to prove she really does care about Michael.
"I didn't feel much when I held Astrid, but I got a good feeling from Holly."
Erin inadvertently revealing that she considers Michael a father figure.
The office showing their appreciation to Michael before he leaves by singing "Seasons of Love" from Rent with altered lyrics to him.
Jim telling Michael that he's the best boss he ever had in the episode "Goodbye Michael".
Also from "Goodbye Michael", Dwight reading the letter of recommendation Michael left for him, letting him finally know how much he was appreciated.
Followed immediately by a game of paintball, and a shared smile in the office afterward. Aww.
And Michaels final goodbye to Pam. The audience don't what they said since Michael removed his microphone, but just the idea that she managed to see him off after he spent the whole episode agonizing over her not returning to the Office in time is heartwarming in it's own.
Michael: Erin, listen to me: you shouldn't rush into this at all. And you know why? Because you are beautiful, and you are fun, and you are smart. And when the right guy comes along, you'll know it. You will. [she laughs, and he kisses her on the head] And you know what? You don't need a mom. Because you have my number, and you can call any time.
One of Michael's last lines in the episode, which just about sums up his entire character: "They say on your deathbed you never wish you'd spent more time at the office, but I will."
Michael telling the party planning committee to plan a party everyone will like. It's nice until we later find out that Michael won't be there, so it doesn't matter what he likes. He just wanted his friends to have a good time together.
In extension, one of Michael's defining traits throughout the series is his forcing himself into being the center of attention in every event he takes part in, even when(or really especially when) the event has little to nothing to do with him. It really shows how far he's come when he takes his last day at Dunder-Mifflin after over 14 years, a day that he'd be perfectly justified in making revolve around him, and goes to some lengths to make it just another day at the office.
The fact that Michael's last, barely audible line is "That's what she said." It's just so heartwarming in a way I can't pin down.
Micheal telling Jim, "Never, ever, ever give up." when Pam gets re-engaged to Roy.
"I think you're a good guy too."
It's also a Tearjerker. When Ryan gets arrested, Holly finds Micheal crying in his office and he chokes out, "I'm just worried about my friend."
Michael glomps Jim after learning that Jim and Pam are engaged.
In Special Project, Dwight admits in a talking head that the Florida team isn't so bad, after all. "Perfektenschlag."
In "Search Committee" parts 1 and 2, there's a very, very minor subplot where Phyllis and Erin wait to see if they are related (Phyllis gave up a child near the area and time when Erin was born). During this time, Erin tries to get back Andy as he politely refuses and tries to get the job of manager. Along with the heartwarming scene of Erin saying that she sees Andy as boss "like a mountain I'm standing in front of" while tearing up, we get Phyllis supporting her in the most motherly way possible, giving Erin love and support she hadn't really experienced as a child. Cut to a talking head of Phyllis saying that the results showed they weren't related. "I'll tell her some other day."
After becoming the new manager, Andy agrees to get a tattoo above his butt that everyone in the office can choose if they fulfill a big sales quota that day. When they do, everyone suggests all kinds of inappropriate and undesirable choices for the tattoo artist as he puts it on. Afterwards Andy sees the tattoo they really selected is of a cute dog wearing a sweater with the word "Nard" on it like Andy's nickname "Nard Dog".
Dwight has the perfect opportunity to get Jim fired: Jim took a week off for jury duty, but Dwight has realized that he actually spent the week at home (he was dismissed from the jury at noon on the first day). After seeing that Andy doesn't have it in him to fire Jim, Dwight decides to go to Gabe, who is at the hospital seeing Angela and her newborn baby. While at the hospital, Dwight discovers that he very well might be the baby's real father. When he finally gets the chance to tell Gabe about Jim's lie, Dwight lets it go, saying that the matter now seems "infinitely insignificant". In his talking head, he explains, "He did it for his kids. I get it."
For this troper, I found it so heartwarming when Pam's sister mistook Kevin as Oscar's boyfriend in the episode "Niagara". Rather than being offended and angry, Kevin's actually flattered and says he'd be "proud to date (Oscar)"