Manager! This is the greatest day of my liiiiiiiiife!!!note Keep in mind that this is, chronologically, the final shot in the series.
Spongebob and Mr. Krabs' reunion at the end of the movie, and Mr. Krabs apologizing to Spongebob for doubting him.
He also says that he'll never doubt him again. Remember who is saying this, and to whom, especially after what he said earlier in the movie and throughout the entire series.
After that, Spongebob finally gets something that he has waited so long for: the manager position at the Krusty Krab 2!
Squidward generously handing over the manager badge. Keep in mind that Squidward hated Spongebob throughout the course of the series. To see him do something nice like THAT is heartwarming in and of itself.
This even extends to the end credits- they depict Spongebob, now manager of the Krusty Krab II, working hard and loving every second of it. It's a simple ending, but satisfying nevertheless, and suiting of his character.
The whole audience in the movie theater - not just the pirates - cheering when the tear of the Goofy Goobers revives Spongebob and Patrick.
King Neptune getting an aesop about showing love and compassion, and praising Mindy for being right.
Near the beginning of the film, Patrick treats a depressed Spongebob to several ice cream sundaes to cheer him up.
The end credits of the film definitely qualify- they depict Spongebob, now manager of the Krusty Krab II, working hard and loving every second of it. It's a simple ending, but satisfying nevertheless, and suiting of his character.
It's a brief moment and easily lost in how sad the scene is, but when Spongebob and Patrick are under the heat lamp, Spongebob's arm snaps off. Patrick, obviously not doing well himself, picks it up and puts it back on his friend.
Arguably, Patrick's Adorkable reaction when he finds out that Mindy knows his name.