Due to my small wrist, my favourite sizes are between 34mm and 38mm. Saying that a lot would depend on the lugs of the watch. On lovely curved lugs, a larger size may be wearable (I had noticed that a Patek 5270 which is 41mm is wearable) whereas if the lugs were straight like say on a Breguet, even a 37 or 38mm watch would be too large on my wrist.
Sham

It depends on when and what you are wearing it for:
Seiko Sumo 45mm - weekend watch
Omega Titanium Seamaster 41.5mm - weekend and sometime work
Rolex Oyster Perpetual Date - 34mm - grandfathers 1964 - work and dress
Panerai (PAM535) - 42mm - weekend watch.
Breitling Colt - 37.6mm - work watch
Here are some wrist shots that I had handy. I have a 7" wrist, approx.
