Let's forget about movement, history, brand, price, etc for the moment and just on design, which is the best designed watch in the category of dress, sport, diving, aviation and casual. For me, they are: Dress: GP 3 bridges Sport: AP RO Diving: Bell&Ross ...
Second I started my answer but realized it ain't sooo easy. So I guess I would just use the stable i.e. in collection. Dress: JLC Ultra thin platinum Sport: Sinn U1 "ultimate tool watch" Diving: Rolex SD 16660 or Panerai PAM 187 1000m or Sinn U1000 Chrono...
I like the u series of Sinn too especially U1. The minimalist design is cool and the lego hand is one of its kind. I like it so much that I have one regular U1 and another black U1 (Tempus version)!!