In a meta example that crosses the Awesome territory - the plot details leaked about a month and a half prior to the game's release and gamers and geeks alike refused to share them, to minimize the damage done to the game's creators.
Out-of-universe example, but the scenery is particularly heartwarming. In most Zombie Apocalypse games, everything is brown, desolate, and dead. There is usually not a plant to be seen. In this game, however, you can see the earth retaking the planet after the collapse of society - the plants flourish, the water is filled with algae. The earth is still alive and thriving, even after such a catastrophe.
Of course in-universe, this is probably seen as somewhat the opposite, since the Infected are using the proliferation of runaway plant life to help spread the infection further. While the Earth is thriving in the wake of the apocalypse, it's slowly killing the human race as a result.
Everything in the first scene showing Joel interacting with his daughter, Sarah. First Sarah giving him the watch, to their playful banter, then Joel carrying his little girl to bed and stroking her hair. Yes it's obviously setting us up for the big Tear Jerker that's to come but, damn it, it's affective.
Joel: Goodnight, baby girl.
When Sarah wakes up, one of the items the player can interact with is the birthday card she forgot to give Joel. Inside, Sarah writes that even though Joel's never around & he despises the movies she likes, he's still the best dad ever.
Joel, Ellie, Henry and Sam sharing a rare moment of respite at the radio tower after escaping Pittsburgh, with Joel telling stories of him and his brother and Ellie returning the toy figure Sam had found earlier and wasn't allowed to keep back when the group first met. It makes what happens afterwardsall the moreheartbreaking.
Although Henry had his gun pointed at Joel, and already fired a shot at him for reaching for his handgun, Joel took one look at Ellie being attacked by Zombiefied Sam and decided to risk being shot. Just to make sure Ellie wouldn't get hurt.
After escaping from the bridge, the player will start finding notes from a man named Ish, who was out at sea during the full brunt of the outbreak. He arrived at a sewer and made a life for himself there and he met a family with kids, whom he invites to stay with him. You'll find that their lives were pretty great, with various rooms for the kids and signs of them cooperating - it's nice to know that there are some hospitable people out there. Then you find Clickers in what appears to be Ish's bedroom.
And then you find a note that shows that Ish, along with a woman and a few kids, were able to escape the sewers alive. And even with all of the trauma that has happened and is still happening to them, Ish genuinely believes that there is still good in humanity, and it continues to drive him onward.
Joel's meeting with Tommy. When they parted ways, Tommy told Joel that he doesn't want to see his face ever again. They have a tearful reunion.
After Joel meets up with his brother Tommy to give him Ellie so he can give her to the Fireflies (which was the entire plan from the start), Ellie runs away because she wants to stay with Joel, since he's the last person she has. After thinking about it, Joel tells his brother to go home and continues with Ellie.
Ellie: Everyone I've ever cared about has either died or left me. Everyone... fucking except for you! So don't tell me I'd be safer with someone else, because the truth is I would just be more scared.
After Joel decides he'll take Ellie instead of leaving her with Tommy, Tommy tells Joel that he doesn't have to leave as there's a place for him at the hydroelectric plant with his remaining family. At the very end of the game, Joel & Ellie are on their way back there.
They might be minor characters, but seeing Tommy and Maria interact together is this. After spending hours in Pittsburgh with the hunters and their dog eat dog/survival of the fittest/women are good for one thing only philosophy, seeing two people that genuinely care about one another is a nice change of pace, especially in a world where that kind of affection usually just costs more scars. Yes, Tess and Frank, we mean you.
Ellie has a series of awesome moments after Joel is Impaled with Extreme Prejudice during a bad fall and needs medical care. She goes out to hunt for food, gets medicine, kills infecteds, fights scavengers and cannibals. All this just to cure Joel.
Not to mention the part when she comes back to Joel, gives him a shot of penicillin, then curls up next to him before falling asleep.
Joel finding Ellie completely broken after she kills David, comforting her with a tight hug and calling her "baby girl" like he used to call his own daughter Sarah. This is the first time in the game we see him fully acknowledge her as a surrogate daughter.
Giraffes in Salt Lake City. After spending literally hours doing nothing but sneaking, killing, running and fighting for your dear existence, seeing spring in all its glory feels amazing. It's also the first time Ellie expresses any kind of happiness after her run-in with David.
Tiny little detail sells this scene: you don't have to take the conversation at all, and if you take it, it's up to you to leave it whenever you feel like it. You can really spend hours standing there, enjoying the view.
Something of note is the stuffed giraffe in Sarah's bedroom at the beginning of the game. It is highly possible that this later scene is meant to help connect Ellie and Sarah and emphasize Ellie's role as Joel's surrogate daughter.
After the major Tearjerker of Ellie trying to provoke a reaction from Joel by needling him about Sarah, and Joel's furious statement that Ellie is not his daughter, seeing the way he gradually opens up to her over the coming seasons is very uplifting. First, while in the University, Joel answers some of Ellie's questions, and perfectly calmly, with no anger or defensiveness, lets her know he wants to stop when she goes too far, and she accepts it immediately, with her voice making it clear that she's going along with him out of respect for his feelings, rather than because she's afraid of provoking another outburst. Later, after they reach Salt Lake City, Joel talks about the loss of Sarah quite freely with her, in a tone that shows he's already covered the subject with her.
Joel finally goes full Papa Wolf in the finale after he learns that Ellie's surgery will kill her and that the cure is just a possibility. He breaks free, tortures a Firefly in the most pragmatic way possible and proceeds through a hospital filled with armed soldiers, in the end defying even Marlene herself.
The Note from Mom. To be specific, Ellie's mother, Anna. It's a message to Ellie about how despite not being fond of children and babies, she still considers giving birth to her the most incredible thing she's ever done in her life. The most touching part is her advice that, despite the apocalypse, to "Find your purpose and fight for it", and "life is worth living". "I see so much strength in you. I know you'll turn out to be the woman you're meant to be. Forever, your loving mother." When Ellie reads it, she says to herself, "I'm trying to make you proud."
In Salt Lake City, if you kill all the Infected in the tunnels, Joel will say, "Endure and survive", one of Ellie's favorite quotes.
Ellie kissing Riley
Ellie and Riley messing about in a photo-booth, taking photos with all sorts of poses.
Honestly, the whole damn time they were goofing around with various things they found kept making this troper smile and laugh.
The brief part where Ellie rides the Merry-Go-Round deserves a special mention. The animation and lighting in those few seconds is just gorgeous, added with the soundtrack "Together" playing in the background.
The story of how a lesbian Gamer's Lets Play of Left Behind brought Ashley Johnson (Ellies Actress) to tears.