This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Sonic Unleashed
Sonic's humiliating defeat in the intro.
Chip's resealing into the Earth. To make things worse, Sonic is completely stoic.
To specify, Sonic sees Chip's form lying on the ground and is about to help him, when the form disappears. As he listens to Chip's final speech, Sonic picks up Chip's remaining necklace and puts it on his wrist. Sonic then watches the sun rise, and allows a smile to cross his face as he thinks fondly of his friend.
During the credits of Sonic Unleashed, the song "Dear My Friend". It's almost kind of a Mood Whiplash since the rest of the game seemed kind of light-hearted, (with Aside Glances, all kinds of little gags during the cutscenes, the cartoony-looking villagers, not to mention the funny promo short: "Night of the Werehog,") then comes the Bittersweet Ending. What really brings it out is the fact that the song is supposedly in Chip's POV, and you know he and Sonic will never see each other again.