The good ending of any route and Kyousuke's last conversation with Haru. Kyousuke's conversation with Maou at the end of the siege might count too but it turns out that it was all a lie and a ruse.
Kanon's ending is pretty notable, too. The last part while Kanon is skating is beautifully heart-wrenching, especially when coupled with a rendition of Songs My Mother Taught Me (appropriately enough).
The very last moments of main story qualify, with a good dose of Tear Jerker.