I'm with Steve on a GMT, as you already have a Submariner. The GMT's are really nice travel watches since the bezels rotate and if you get a model with the 3085 or later movement the independent GMT hand enables you to keep track of three timezones. A very handy feature if you do business in multiple timezones or travel across multiple timezones. The Explorer's fixed bezel makes it less handy. The 16760 "Fat Lady" can still be had relatively inexpensively and was produced for a relatively short period of time, making it relatively rare and if you want beautiful ask Steve to post a pic of his Root Beer nipple dial GMT.
The other one I'd look at is the Daytona. Maintenance costs are higher, but these are beautiful distinctive watches. The Zenith derived movement watches have been rising in value over the past years.
Lastly, if you want a Sub on steroids take a look at the Sea Dwellers. These are the professional dive watches in the Rolex line. They are beefier and more tool like than the Subs. Personally I've been looking for a 16660 these days, but unfortunately the window seems to be running away from me, as they are getting harder to find.
