I've seen some pretty depressing films in my time (Melancholia being the winner of that particular award) but I have to admit that I wasn't quite prepared for the stark realism of Michael Heneke's Amour.
The film tells the story of an elderly Parisian couple named Georges and Anne. One day, Anne has a stroke and becomes mentally and physically disabled. Georges now must take care of her. In a deeply sad way, the film depicts her slow descent into infirmity and, ultimately, death.
With its typical European existentialism, Amour moves slowly in both theme and style. The camera lingers without a cut on many shots much longer than it seems it should but that is Heneke's point. He successfully illustrates the physical, mental and emotional strain of end of life care. It's a tough film to watch for a number of reasons but well worth it as I walked out of there realizing that my wife and I are woefully behind in our later life planning.
I'd recommend Amour only if you are prepared to watch a slow and maudlin film.