In the Mood for Love

In The Mood For Love (original title: 花樣年華) is a movie by Hong Kong art-house director Wong Kar-wai, who had previously made a name for himself with the critically acclaimed Chungking Express in 1994. Released in 2000, it is set in the early 1960s and tells the bittersweet story of a man and a woman (played respectively by Tony Leung and Maggie Cheung) who are neighbors, and whose respective spouses have an affair with each other. While they find themselves increasingly attracted to each other, they refuse to give in to their feelings out of a sense of propriety.

It is the second part of an informal trilogy of films. The first, Days of Being Wild (1991), was (partly) about Maggie Cheung's character from this one. Tony Leung also appeared in an uncredited cameo, but it's unclear if he was playing the same character. The third film, 2046 (2004), is about Leung's In The Mood For Love character, with Cheung briefly appearing in flashback. Though thematically similar (as is much of Wong Kar Wai's work, which very often deals with the difficulty of finding love), the films don't have much in common story-wise. 2046 might spoil In The Mood... a little bit, but otherwise they're separate experiences.

Tropes used in In the Mood for Love include:

Bittersweet Ending
Completely Different Title: The original title translates as "Our Glorious Years Have Passed Like Flowers".
The Faceless: Neither character's spouse is ever shown; we only hear their voices or see the back of their heads.
Fetish Fuel: If you like to see women wear form-fitting qipaos, this movie's for you.
Hong Kong: That's where the story takes place, but since it's set in the early 1960s and the city has changed a lot since then, the movie had to be shot in Malaysia.
Landmark of Lore: The epilogue of the film takes place in Angkor Wat, a place where Mr. Chow feels he can safely unburden himself of his secret.
Scenery Porn: Angkor Wat (that's assuming every movie photographed by Christopher Doyle doesn't automatically qualify).
Slow Motion: Maggie Cheung is repeatedly filmed in slow motion while walking, climbing stairs, buying dumplings, etc...
Titled After the Song: "花樣的年華" (Hua Yang De Nian Hua) is a song by Zhou Xuan, while the international title is from the song "I'm in the Mood for Love".
Unlimited Wardrobe: Maggie Cheung wears a different qipao in every scene, and sometimes even within what seems to be one scene, hinting the two of them are playing out various scenarios more than once.
UST: The whole plot.
Will They or Won't They?: A good question. Many viewers have admitted impatience that the protagonists would get it on already.