An underscored one for Elizabeth in the 2011 E3 gameplay demo: at the beginning of the demo, after Booker and Elizabeth manage to hide from Songbird, she asks Booker to kill her if there is a minimal chance that Songbird might take her, pretty much implying that being with Songbird is a Fate Worse than Death for her. When Songbird nearly kills Booker, she decides to let Songbird take her to save Booker. And the last thing Booker sees of her is her crying face while she tries to reach for Booker.
And then, Booker, injured as he is, goes after the two of them without giving a damn about the fact that he almost effing died, and jumps onto an air rail.
Elizabeth dancing to live music for the first time. She just looks so happy.
The game's stinger. Booker comes to in his office, back in 1893 and hears Anna crying in the next room. You take control of him and get to open the door, while he calls her name, and then the screen fades to white. The obvious implication being that, in one reality at least, Booker got to be with his daughter and will be able to raise her in a happy and loving way
And, presuming that Booker has residual memories of the events of the game, when she's older he'll be able to take his daughter to Paris just like he promised.
How easily Booker switches to Papa Wolf mode when he realizes who Elizabeth is. He's truly an opposite of Comstock in every way, ability to care for the daughter he never realized he had included.
The insert during the credits of live-action Courtnee Draper and Troy Baker working on "Will the Circle Be Unbroken" is quite touching and shows how much love was put into this game.
While very emotionally restrained (to the point of snarky), deep down Rosalind seems really happy to have her "brother" Robert along.
Her Voxophone entries make it very clear that she cares deeply for Robert; hell, the entire reason that she's even doing any of this to begin with is because Robert insisted on it, and because she'll lose him if she doesn't.
Rosalind: (after their "deaths") But my brother and I are together, and so, I am content.
Rosalind: My brother has presented me with an ultimatum: if we do not send the girl back from where we brought her, he and I must part. Where he sees an empty page, I see "King Lear". But he is my brother—so I shall play my part, knowing it shall all end in tears.
A Voxophone available in the Clash in the Clouds DLC reveals Rosalind transfused her own blood into Robert while he was still hemorrhaging and out-of-sorts, and rehabilitated him using music. There's just something... sweet about that.
Elizabeth singing to a scared kid while Booker plays a guitar. If you try to steal stuff in the place and killed ten men and the kid was hiding from the gun fire.
Preston E. Downs is an amoral bounty hunter hired to kill Daisy and in an alternate universe Booker. After he sets some bear traps for Vox messengers, he learns that Daisy is using kids as messengers in the worst possible way. After having to amputate a Native Americans boy's leg and effectively adopting him, he runs into that universe's Booker. And finds that he speaks Sioux. And learns how Columbia treats Injuns and crippled kids. And resolves to scalp Comstock. With the kid's help. This is soured by the fact that he takes over the Vox after Daisy dies.
Take a look the second time Booker sets coordinates in the First Lady airship. After trying to trick Elizabeth the first time, the next he sets it to go to Paris like he promised her.
Towards the end of the game, all he wants to do is take her to Paris and forget about Columbia.
The couple from the "marriage" raffle in the beginning of the game thank you later on in Battleship Bay if you choose not to "cast the first stone" at them.
In the Battleship Bay section when you see Duke and Dimwit for the first time, Elizabeth will sometimes wander around holding Cotton Candy. She doesn't comment, but it's adorable.
Actually, at least on the Boardwalk, she can get cotton candy again and comment on how much she's missed out on. Which is a bit of Tear Jerker.
During the first odd desaturated segment were you're at Booker's office, you hear Robert slamming on the door, yelling that "they had a deal". Booker's responds that he's not going to go through with it. It's nice to know that he didn't want/wasn't going to go through with selling Anna. Unfortunately, this is not particularly meaningful until a second play through.
In the second such segment, Booker demands they promise not to hurt the girl if he brings her to them. Comstock may have smashed that promise to shreds, but it is nice to see Booker try.
Elizabeth finally burying the hatchet between her and Lady Comstock. Although Elizabeth was fully willing to defile Mrs. Comstock's grave and body just an hour earlier, she learns enough about her in the interim to develop genuine sympathy for the woman. Given the prevalence of hatred between characters and factions, it was poignant to see two people resolve their grudges with mutual respect.
Lady Comstock's story herself. In her youth, she was known to be a cruel woman, who would manipulate others to do her bidding. In her own words, "there was no pain that she would deny them." When she had burned all of her bridges, Comstock offered her forgiveness, and she became devoted to him. She was devastated when she discovered the truth behind Elizabeth, and decided that truth came with forgiveness. Later in the game, she overjoyed at the prospect of other worlds, because there could be one in which she redeems her husband.
At one point, the player is given prompts to "Help Elizabeth" and "Tie Corset". Becomes Heartwarming In Hindsight when you realize that Booker is helping his daughter get up and get dressed, something he never had a chance to do.
As bittersweet as the ending was for Booker and Elizabeth, it was truly uplifting for everyone else you saw, met, and fought throughout the game. The child Elizabeth sang to, the soldiers suffering "tear sickness," The Handymen, Mr. and Mrs. Lin, Slate, Daisy Fitzroy, Lady Comstock, every innocent victim of Founder oppression or Vox violence, and everyone you killed throughout the game will now receive a second chance in a world without Columbia.
True, but “no Columbia” also grants life to those who were never born because of its existance. Also, Since Comstock was prevented from existing in 1890, and the game starts in 1912, anyone more than 20 years old should be fine.
And even then, everyone has an alternate reality counterpart in this universe, so, yeah, EVERYONE gets a second chance.
When the player possesses a Motorized Patriot, they will occasionally shout "For family!" This is given extra weight when one has experienced the ending of the game.
Booker's Heroic Sacrifice. Booker is unquestionably a Bad AssOne-Man Army. He shouldn't have any trouble wrestling 3 girls as small as Elizabeth/Anna from holding him down and drowning him but he doesn't even fight it. He lets himself die to ensure that Comstock never exists to threaten his daughter.
A very small detail, but the inclusion of this gay couple among the myriad NPC's in Rapture. They're just so sweetly posed. You'll also see high-society NPC's of all races socializing as equals- a big difference from Columbia's pervasive, enforced racism.
While not calling him by name, for obvious reasons, Elizabeth refers to the Booker from the game proper as her father. It shows that she still loves and appreciates the man, which highlights the emotional disconnect between her and the player character, and it's an early sign that there's something off about your Booker.