Melancholia

This was, for me, the most spectacularly ambitious movie of the year. From it's brilliant painterly prologue, to it's inevitable, cataclysmic finish (that's not a spoiler here, it's in the aforementioned prologue), Melancholia is one of the most exhilarating cinematic experiences I had all year. If I were in the business of giving awards, Kirsten Dunst would have the performance of the year award from me for her work here.
I really would love to write more about Melancholia and how beautiful the whole thing is from start to finish, but honestly, Kim Morgan wrote a mini-essay for MSN Movies top 10 wrap-up (expanded and expounded upon at her own blog) that so wonderfully encapsulates most everything I'd say anyway and much more, I shudder to think how much my piece would pale in comparison, so just read hers.
Now here's Kim (excerpted):

Universal and personal, blatant and mysterious, sorrowful and funny, nihilistic and yet, sublimely, romantically, celebratory, Lars Von Trier’s 'Melancholia' takes the black bile of its namesake -- the depression of its heroine -- and transforms the “humor” into exaltation. A planet -- a terrifying, dazzling planet that, true to Dane Von Trier’s inspired swan dive (black swan dive) into German romanticism, is set to destroy life on earth: Götterdämmerung via "Tristan and Isolde" (which he uses in the picture’s rapturously beautiful overture), via Ophelia via Cassandra via Von Trier’s own personal mythology.  

And then comes planet Melancholia, inching closer and closer, leaving stable sister Claire (Charlotte Gainsbourg) panic stricken while Justine, calmly, grimly and at times, cheekily, accepts annihilation, not as easy suicide but as a kind of cosmic extension of despair. Yes. Finally. Justine isn’t wallowing in depression, she’s embracing, seducing it, and in one of the picture’s most exquisite moments, lying beneath it naked -- basking in the glow of doom.  

With 'Melancholia' he grants depressives a gift. Taking Justine’s depleted darkness and imbuing her with celestial life through doomsday, he, to recall another German Romantic, creates an Ode to Joy through heartbreaking and gloriously inspirational…woe.