I agree with three that have been talked about here.
(500) Days of Summer was so well done, and will leave you with a happy, lovey-dovey feeling.
Red Roses and Petrol has the fabulous Malcolm McDowell.
Pieces of April was wonderfully dysfunctional...actually so was Red Roses.
Next Stop Wonderland is one that I haven't seen in a long time, but I remember finding it to be quite good.
So there are some choices, depending on your mood.