Izumi's dream/vision of Toyama. Doubles as a Tearjerker.
The brief flashback/residual haunting of Kayako and Toshio in happier times. Toshio is seen running into the kitchen and showing Kayako a picture he drew, while she smiles and admires it.
The scene with Toyama and a younger Izumi, when she shows him a picture of angels that she drew in the sand.
YMMV, but Toshio's little smile when Kobayashi shows him a picture that the former drew of Kayako and Takeo. It's the only time in the entire series that Toshio is shown genuinely smiling.
Depending on your point of view, Toshio's presence during the birth scene could be considered this, in a twisted, disturbing sort of way. He's just so happy to see his mother being reborn (in a sense).
The moment in the fourth movie in which a haunting/past event depicts a touching mother/son moment between Kayako and Toshio is extremely sweet.