Although it may not be one of the most illustrious G's on the market, I would wager that Casios most basic current G-Shock, the DW-5600E, is the biggest seller of the range.
As far as reviews on the net go, it seems to be a bit of a wallflower, so I thought I would share some impressions for those who might be interested.
I won't go into too much detail about module #1545 and the 5600E's technical specs, as they are readily available elsewhere - but allow me a few observations. The display is very crisp, and uncluttered by G-Shock standards. Turning off the 'backlight function' (you can still use the EL backlight normally, it just won't flash when the alarm goes off) means one pictograph less on the face, and a somewhat cleaner look.
The buttons are fairly accessible but firm. They are slightly recessed from the outline of the case and would be very difficult to depress accidentally. The top left button, used mostly to set the time, is recessed somewhat deeper than the other three buttons - a nice touch, and exemplary of the thought that has gone into the design of this watch.
By my measurements, the case is 43mm wide and 14mm thick, and the lugs are 16mm apart. The top of the strap itself is about 27mm wide where it meets the case. The top of the strap and the case fit almost flush, so there will be less danger of snagging the case on anything. The rest of the strap tapers down to about 19mm. The strap is very ample (I have 8 holes free on my 6 1/2" wrist!), and made of a comfortably soft resin.
What do I miss? Well for a start I'd much rather that the DW-5600E had more than just one daily alarm. I would also prefer a 60 minute countdown timer in increments of full minutes instead of the 24h timer with seconds - I appreciate I may be in a minority on this point but I use the timer a lot and feel it could be easier to set. In common with most G-Shocks (and most other digitals for that matter), the functions are not particularly intuitive to use. Still, it's not exactly rocket science and I'm sure devotees of the G can get everything done blindfolded.
I believe the oldest DW-5600E's are not yet 10 years old, and I cannot say how the resin of bezel and strap will hold up to to the test of time. Replacement bezels and straps for this model are however readily available.
The overall build quality of the watch is hugely impressive, and it is very comfortable to wear. I believe they can be picked up from online vendors for USD 30 - 40 shipped. For some reason, European vendors rarely seem to stock this model, although I have seen other variations (negative display and textile strap) for sale in Germany.
Mine is a used, Malaysian made model.
Whether it's old-skool nerd appeal, anti-hero understatement or just the need for a no-nonsense watch, I think the DW-5600E can deliver.