2. The Apartment (1960)
Shirley MacLaine originated the "run to the one you love on New Year's Eve" sequence (which Billy Crystal perfected in When Harry Met Sally... and Renée Zellweger attempted in Bridget Jones's Diary) in this Billy Wilder classic, in which office shnook C.C. Baxter (Jack Lemmon) lends out his Upper West Side bachelor pad to his philandering bosses in an effort to quicken his climb up the corporate ladder. But when he falls for one of big boss man Jeff Sheldrake's flings (MacLaine, as elevator operator Fran Kubelik, in her second Oscar-nominated performance), the situation gets precarious.
The love triangle comes to a head on New Year's Eve, when Baxter refuses to give Sheldrake access to his love nest and ends up quitting his job. As the clock nears midnight, Fran—observing the holiday with Sheldrake in raucous Mad Men style—realizes that it's Baxter she loves.... (Cue the aforementioned running sequence.) The film ends with a celebration a deux, complete with champagne and gin rummy, in which Baxter tells Fran he loves her and she responds with one of the most memorable final movie lines ever: "Shut up and deal!"