My two favorite Zimmer scores (I don't believe in saying "Best" - it's all opinion) are apparently outliers - Broken Arrow and Inception. At least Solium mentioned BA. I think they are both perfect for their films and great on their own - though Broken Arrow works better for me in its original version.
But there are quite a few mentioned here I love, and some I just don't know well enough (like Beyond Rangoon and The Thin Red Line).