This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / How the Grinch Stole Christmas!
The book and TV special:
"Santy Clause, why? Why are you taking our Christmas tree? Why?"
The song "Where Are You Christmas" is a combo of heartwarming and tearjerking. Little Cindy Lou sings about her Yuletide doubts. They don't get some grown-up to do it as a background song, either - that's Taylor Momsen. She looks at her small stocking, and a list saying "Dear Santa, I don't know what to ask for this Christmas." She looks at Mount Crumpit far away. And with the last few notes of the song, we see the Grinch entering his lair, all alone. Tell me that at some point that didn't twang your emotional strings. The lyrics can especially hit home for older viewers — with Christmas not being the same as it was when they were kids and missing it.
After he's had his Roaring Rampage of Revenge on the schoolkids, him struggling to climb up the mountain while uttering how much he hates Christmas, coupled with the soundtrack, is nothing short of heartbreaking.
The look on young Martha's face when she picks up the Grinch's broken present.
For the first time in his life, the Grinch was excited about Christmas. He made his own gift for Martha (Sure, he made it from stuff he broke, but it's the thought that counts), and even the old ladies who looked after him told Cindy Lou how nice it was to see him in the spirit. All he wanted was to look nice when he gave Martha his present...
The final moments of the flashback wherein the little Grinch struggles to climb away up the enormous snowy mountain, screaming to himself about how he hates Christmas, before eventually standing alone on the mountain. None of this is helped by James Horner's weeping score.
From the extended version, Martha and Betty are seen competing in the lighting contest. When Betty lights up a spectacular display of Christmas lights, the judges are very impressed and write her name down as the winner, which would finally make Betty's dream of having the best Christmas light display in Whoville and beating Martha come true. But Mayor Maywho plays favorites and, trying to butter up Martha for the later marriage proposal, claims that it's a "split-decision" and declares Martha the winner, leaving Betty feeling disappointed and crushed, and showing just how corrupt the mayor is.