Near the very end of the film when Fischer Jr confronts his father in the strongroom. His father starts to speak, and is only able to utter the word "disappointed" before his son finishes the sentence with:
Fischer, Jr.: I know, you're disappointed that I didn't turn out to be like you. Fischer, Sr.: No. No, nonono. I was disappointed... that you tried.
Then, before Fischer Jr.'s father dies, he has his son open the safe containing his most prized possession: the pin-wheel he gave his son as a child.
Not so heartwarming once you realize that the whole thing is a lie, designed to help Saito's business domination. Then again lying people into heartwarming is Nolan's trademark.
Does that really matter? He'll still continue his life feeling a lot better about his father, who cares if it was true or not?
The coup de grace on the scene is Cillian Murphy's delivery. A perfect, red-faced, choking-back-Inelegant-Tears face that is so heartrendingly relatable that you'd think it was his real father that had died.
Add to that that this was Pete Postlewaite's last movie, as he died shortly afterwards.
The end is a series of this.
When Cobb finally wakes up in the plane, the camera shows Arthur and Ariadne, looking at him and smiling as if to say "well-done", then Saito, waking up... and immediately reaching for the phone to make that one call. You feel Cobb's relief as your own.
Then in the airport, at the customs, Cobb has to wait only a couple of apprehensive moments before the guard stamps his passport and says: "Welcome home, Mr. Cobb."
... immediately followed by Ariadne smiling at Cobb again, and then as he walks out of the airport, he passes all the other team members, also looking happy, and finds his father-in-law waiting for him at the arrival gate, to take him home.
And then the very end scene, in which Cobb is reunited with his children. Once again there's a moment of hesitation as he watches his children turn around, and then he sees their faces for the first time since he was forced to leave them. He then rushes forward to play with them and leaves the totem behind, showing that it no longer matters to him whether he's in reality or not—as long as he's with his children, he's happy.
The top wobbles. Let that sink in.
A sort of Fridge Brilliance sets in when you realize that Dom and Mal lived with each other essentially for a lifetime inside their dream world. Even after getting back to reality, they're still deeply in love with each other and want to spend another lifetime together! That makes Dom and Mal's marriage one of the happiest, and makes what eventually happens all the more tragic.
Shortly before that, the whole speech about how wonderfully complex the real Mal was, and even with all of Dom's imagination, he could never truly recreate her. Made absolutely crushing in the fact that all of these heartwarming things are only being said because Dom is finally able to let her go.
Cobbs line about positive emotions trumping negative emotions, he just states it like scientific fact.
Related Fridge Brilliance: Cobb knows that an inception can grow until it becomes part of the host's personality, and he doesn't want Fischer to suffer because of him.
Robert Fischer did not give the slightest fuck about being kidnapped by armed men...until he heard Browning screaming.