While there were a lot of films that pushed the bounds of what some people believed to be morally acceptable, some films helped signaled the end of the Pre-Code era. Tarzan and His Mate (1934) was a sequel to the extremely popular Tarzan, the Ape Man (1932). The films starred Johnny Weissmuller as Tarzan and Maureen O’Sullivan as Jane. They were clearly in a unmarried relationship and in Tarzan and His Mate Tarzan and Jane go for an extended naked swimming scene which after the public outcry of several religious institutes was removed from the film.
Eventually fear of government control and the constant outcry of various religious groups lead to the formation of the Production Code Administration. The Legion of Decency kept watch and over the years would protest films that they felt were immoral and condemned them as they saw fit.
Condemned films include Blood Money, Design for Living , Extase, Grandeur and Decadence, Queen Christina, The Worst Woman in Paris, Finishing School, The Life of Vergie Winters, Madame DuBarry, Men in White, One More River, Riptide, The Scarlet Empress, Damaged Goods, Strange Cargo, This Thing Called Love, No Greater Sin, Two-Faced Woman, Volpone, White Cargo, The Outlaw, Mom and Dad, Black Narcissus, Forever Amber, Three Daring Daughters, Bitter Rice, M (1951), The Miracle, The Moon is Blue, The French Line, Rififi, I Am a Camera, And God Created Woman, Baby Doll, The Seven Year Itch, Love in the Afternoon, Some Like it Hot, Breathless, Never on Sunday, Psycho, Spartacus, A Cold Wind in August, Jules and Jim, Viridiana, Boccaccio ’70, 8½, Kiss Me, Stupid, From Russia With Love, Of Human Bondage, The Pawnbroker, Blowup, Masculin, féminin, Torn Curtain, Hurry Sundown, A Fistful of Dollars, Reflections in a Golden Eye, Rosemary’s Baby, The Good, the Bad, and the Ugly, The Odd Couple, I Am Curious (Yellow), A Clockwork Orange, The Last Picture Show, Billy Jack, Last Tango in Paris, The Wicker Man, High Plains Drifter, Rocky Horror Picture Show, Lemora, The Outlaw Josey Wales, Carrie, The Omen, Grease, Dawn of the Dead, All That Jazz, American Gigolo, Dressed to Kill, Friday the 13th, Little Darlings and Used Cars.
The infamous swimming scene from Tarzan and His Mate.
Something for the ladies, the locker room scene from Search For Beauty (1934). A film about a fitness magazine that becomes a skin rag.
The Marijuana number from Murder at the Vanities (1934)
For a complete list of pre-code films, you can look here. Also there are several box sets that different studios have released in the past couple of years that are excellent. Universal Studios have released the Pre-Code Hollywood Collection and Warner Brothers have released three Forbidden Hollywood collections.