I believe the movie that had the most surprising ending was Patrick Garland's A Doll's House, a 1973 film based on Henrik Ibsen's 1879 play. Ideally it would have had a happy ending--for the family at least. However, it was a rather sad ending for the family.
All the fairy tales we read as children have happy endings. Cinderella gets the prince; Bambi grows up and finds someone to love, and the Little Mermaid gets to be human and marry the man she loves. As we grow up, we find that life is not always about happy endings. I guess this is why Ibsen's A Doll's House is not read until college.
I was surprised by Nora (Claire Bloom) leaving Torvald (Anthony Hopkins) and her children because throughout the movie I could tell how much she loves and adores them. She was always playing games with them and buying them gifts. It really showed how much she loves them when she continues to buy them gifts even though she needed the money to pay off her secret loan.
I could have understood Nora deserting her family if Torvald had not apologized for his erratic behavior. However, he did apologize and swore that he would forget the whole situation ever occurred. This was Nora's chance to stay and raise the children she loved and live with her husband, who was willing to give her most anything she wanted.
In the end, Nora decided to leave her children and husband and start a new life back in her hometown. The saddest part of the ending was that she left the children with their father, who had no idea how to raise them. So, the children would have to be raised by the nanny (Edith Evans). They would never know the love a real mother could have for them.
I felt A Doll's House should have employed a happy ending, but perhaps the personal lives of the main characters did not allow for the understanding needed to make their marriage work any longer. Therefore, the happy ending was omitted, and a sad one replaced it.