Most folks seem to prefer G-Shocks that are large and chunky. As a result, most of the G-Shocks that Casio markets are of that configuration. However, there are a few models that have smaller form factors (e.g., the 5600 series models, the M850, the 7710, etc.).
If you're aware of others, I'd like to know what they are. I'm particularly interested in watches having widths between 42mm and 48mm.