Watching Sam and Oda Mae's relationship evolving from mutual annoyance to mutual fondness and respect.
When Willie shows up at Oda Mae's place, Sam yells at her to "Get out of here, fast!", then puts himself between the two of them, even though he can't offer any protection.
Later, when he realizes that Carl and Willie are going after her, he panics and hauls ass to her place to warn her.
Their final exchange upon seeing Heaven itself. Bear in mind, this is the first time Oda Mae has ever seen Sam's face in person (though she had seen his photo in an earlier scene) and could talk directly to him:
Oda Mae: They're waiting for you, Sam.
Sam: I'll miss you. Your mother would be proud.
Oda Mae: I'm gonna miss you too, Sam. You're all right.
Sam's brief bonding with the Subway Ghost when the latter teaches him how to touch things. While he pulls a Drill Sergeant Nasty at Sam it slowly goes over to friendly banter. The Subway Ghost even genuinely nods impressed like a proud teacher when Sam manage to kick a can.
Earlier in the film right before Sam discovers the truth, he tells Carl to "Be careful" when he thinks he's confronting Willie.
Before he realizes he's dead, Carl is actually happy to see Sam again. It went to show that even though he got him killed, Carl did deep down still care about Sam—and the fact that the plan was never to kill him shows that as well.
The Broadway theater version is even better: Although it's futile, Sam attempts to save Carl from being dragged into Hell.
A behind-the-scenes example. The producers auditioned every black actress in Hollywood for the part of Oda Mae exceptWhoopi Goldberg, not wanting her for the part. After Patrick Swayze was cast as Sam, he insisted that Goldberg (whom he didn't even know personally) be given a screen test, considering the part tailor-made for her and threatening to walk if she didn't. Naturally, the screen test was a smash and she got the part, and with it the Oscar. Goldberg and Swayze became close friends and remained so until his death.
