Here's an unconventional one: A man (I think he's a janitor) takes a lunch break in a grey, artificial plaza with a sickly tree in it, thinking about deforestation. Suddenly the tree starts to grow, sending out roots and tendrils to the cracks in the paving, and the janitor climbs up on a branch and helps the tree break through the glass ceiling, laughing aloud as it begins to rain. My description does not do it justice.
Seconding this. In a book full of things that made me smile, that one scene still stood out. That and the one mentioned below with the soldier.
Crowley rushes into the burning building to save his friend - to save Aziraphale.
Debatable - they're both immortals, and Crowley is in a panic, on the run from the Dukes of Hell, and is clearly rushing to find Aziraphale due to not knowing who else to turn to. However, Aziraphale dying at this point would mean that he's unlikely to acquire a new body anytime soon which, seeing as the world is about to end, means they'll likely never see each other again. So while there's no reason for Crowley to have been concerned for Aziraphale's wellbeing, it is heartwarming how desperate he is to stay together with him.
Even without any of that being taken into consideration at all, it's clearly stated — with emphasis — that Crowley was looking for help. When a war between Heaven and Hell was on the verge of breaking out, with demons and angels about to make the leap from 'casual enemies' back to 'full-scale soldiers in active battle to the death', Crowley's instant response was to find Aziraphale — no, not to finally kill his Enemy of six thousand years, but rather to find an ally. It did not even occur to Crowley that their Arrangement might in any way be changed or rendered null and void by the looming war between their respective sides. True Companions!
And relatedly, that when Aziraphale figures out where the Apocalypse will begin, his first instinct is to call Crowley.
He ought to call Heaven. He wanted to call Crowley.
Sergeant Deisenburger being sent away... to the farm where he grew up, and it seems like he's not leaving this time.
I love the bit where he hangs up his gun and stops talking like a soldier. It makes me smile
"The tape he put on was Handel's Water Music and it stayed Handel's Water Music all the way home." The perfect finishing touch to everything that had come before.
At the end, Crowley and Aziraphale get their dinner at the Ritz... And meanwhile, a nightingale sings in Berkley Square.
This troper gets a warm feeling from how Crowley and Aziraphale deal with each other towards the end, e.g. how hands-on they are with each other - Crowley grabbing Aziraphale's arm and whispering to him, Aziraphale laying a hand on his shoulder, etc. Aziraphale expresses genuine sympathy for Crowley's ruined car, whereas Crowley sincerely commiserates on Aziraphale's lost books. Remember that it's an angel and a demon we're talking about here! Representatives of two opposing sides that hate each other so much that the mere tension between them keeps trying to bring about the end of the world.
Crowley is clearly stressed over the idea that Hell could crush and torture him into nonexistence any time they liked, and while he seems to occasionally take it out on humans by making their lives somewhat miserable, he's still willing to lay his head on the chopping block (despite express warnings by Hell that if something goes wrong, he will be done for) to try and prevent the Apocalypse rather than let all those people die for some cosmic chess game. There's also the fact that the war would mean either his own death or the death of his best friend.
At the end, Crowley and Aziraphale choose to stand together in a futile battle against the Devil to try and postpone the inevitable rather than watch him and Heaven wreak havoc on Earth.
The way that Adam Young's love of his home is depicted is very touching, especially when it brings him back from the brink of bringing about The End of the World as We Know It.
Likewise the fact that an idyllic childhood and life among humans (without any celestial or infernal intervention) was able to overcome Adam's demonic nature and instill a love of the world forms the core of the book. Choice and the potential for good and evil in all of us is a big theme of the book best exemplified in truly heartwarming fashion by Adam Young.
A good example: when Adam meets Anathma, she invites him in, gives him lemonade, and spends the afternoon telling him about paranormal things, which fascinates him to no end. He wants to do something nice for Anathma, just because he likes her, so he uses his powers to shut down a nearby nuclear power plant (which he knew she didn't like).
The International Express postman's been delivering items to the Four Horse Persons throughout the entire book and having just finished with Pollution realizes his next stop is Death. Before he goes to meet him, he leaves a final message for his wife saying: I love you. It's sadly very sweet coming from a man who's been helping to reequipped the major players of the Apocalypse.
Which makes his resurrection at the end of the book all the sweeter. Gosh, but it was good to see him alive.