This is an interesting question, and a tough one for me. I try not to have any one "favorite", but the question is a bit more nuanced than that, isn't it? Takes some thought. A few contenders come to mind for me, but the two that are duking it out in my estimation right now are the A. Lange & Sohne Cabaret in rose gold with a black dial and the JLC Reverso Chronographe Rétrograde in rose gold from 1996. Both are shaped watches with elegant, well-proportioned cases and shaped movements, both are hand-wound, and both are in my favorite precious metal. Both were also significant in the history of their respective companies and are no longer produced: the ALS comes from early in the company's modern revival, while the JLC is part of a series that reestablished the Reverso as a medium for important complications. They are both watches that I became aware of early in my watch-loving experience, and both seemed completely out of my reach while they were in production.
Yet, yet, while the ALS wins in terms of overall refinement and movement finishing, the coin lands in favor of the Reverso - at least for today. Why? For one there's something seminal in JLC's recognition that the rotating case on the Reverso offered a special means of expressing a complication. That the Chronographe Rétrograde was released as a limited edition in the series commemorating the 60 year anniversary of the Reverso also makes it something of a celebratory piece. Then, while not as finely finished as the German silver movement in the Cabaret, the JLC caliber 829 has got to be one of the very few shaped, hand-wound column wheel chronograph movements made, and, I imagine, one of the smallest as well. JLC's decision to expose the movement's gilded plates, wheels, and bridges without a conventional dial is the frosting on the cake. Watching the chronograph movement in action is simply mesmerizing.
So there you have it. (Mind you, I might answer differently tomorrow. Besides the Cabaret are such contenders as the Arnold & Son Time Pyramid, the Roger Dubuis Sympathie S34, the JLC Duomètre Unique Travel Time, and the Patek Philippe Cronometro Gondolo 5098R.)