This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / E.T. the Extra-Terrestrial
The moment Mary discovers E.T. He pitifully reaches his arms out toward her and says, "Mom."
"We're sick. I think we're dying."
Every last second of E.T.'s Disney Death. The scene of him dying on the table, while Elliott stretches out his hand and tearfully begs him to stay with him, is just heartbreaking. There's also the fact that as he's dying, Elliott is getting better. Just think how guilty Elliott would have felt if E.T. had actually died...
When the scientists are trying to give CPR to E.T. All you want to do is jump in the TV and push them away. Spielberg deliberately filmed the scene so it looks like they're hurting ET rather than trying to save him, since that's what any kid like Elliot would naturally think. Then there's Elliott screaming for the scientists to leave E.T. alone... then just crying when it looks like he's actually dead...
In addition, the single shot of Gertie jolting and then crying as she watches the scientists defibrillate E.T. is probably one of the biggest Gut Punches in cinematic history (due in no small part to the fact that Drew Barrymore wasn't actingat all! She genuinely thought that poor E.T. was suffering).
The novelization makes it worse. In the book it's made very clear that the only thing keeping E.T. alive at that point is his psychic/empathic bond with Elliot, and E.T's in such terrible shape that it's just barely keeping him going. What's worse, the bond is draining Elliot so badly that he's near death as well. E.T. DELIBERATELY cuts the connection so Elliot won't die with him. That's why E.T. just flatlines while Elliot pops right back up.
Michael, a mature teenager, curling up among the stuffed animals in the closet to cope with his overwhelming concern for his younger brother. But then he sees the flower E.T. revived dying and then realizes what's happening. The Big "NO!" he gives especially tugs the heartstrings. And the very next scene afterwards...
"Look at what they've done to you. I'm so sorry. You must be dead... because... I don't know how to feel. I can't feel anything anymore. You've gone someplace else now. I'll believe in you all my life. Every day. E.T... I love you."
The ending, as E.T., about to depart, says goodbye to Elliot.
If you're not already sobbing the moment Elliott steps up to E.T. and John Williams' music swells up, the long goodbye hug E.T. gives Elliott will seal the deal.
And the way they both say "Ouch".
And how E.T. asks Elliott to come with him.
Not to mention the reactions of Gertie, Michael, and even Mary to all of this.
The worst part? According to Word of God, none of the children were acting. They had to act through the movie in a chronological order and never saw the E.T. costume without an actor inside (let alone the actor without the costume). When the ending was filmed, they had actually befriended the alien and now had to say goodbye forever. Their heartbreak was real.