Die Hard With a Vengeance

John McClane commandeers a taxi so he can race across NYC to stop a bomb attack.  The cabbie's keychain reads "Read Holy Qur'an The Final Revelation".  The film definitely made a point to emphasize the diversity of New York and this is one more little detail for that end.

Joker

Arthur Fleck's (Joker's) keychain is just a ring. Boring and empty. No wonder he was so depressed OR is it a reflection of society's emptiness encapsulated in the palm of his hand???? Makes you think...