So far my favorite has been Climax of the Covenant. Although somewhat difficult to get through parts, it was very worthwhile and I have a feeling it will be a reference to me for years to come while pondering the particular passages tackled by Wright in this book.
ah, least favorite, now that is interesting. I would say my least favorite so far has to Evil and the Justice of God, because parts of it read more like political propoganda than theology.