Another incredibly subtle detail that I've grown to love is the blowing trash. When Jack and Ennis are parting, after they come down from the mountain, right after Ennis says, "Well see you around, huh?" there are two little bits of trash that blow across the scene behind Jack. One is black, the other white. That's the sad part...
But then, we see them again! Behind Jack as he rushes to meet Ennis again after four years apart!! That's the happy part!!