It looks like Simon Pegg, in the movie Mission: Impossible 4: Ghost Protocol, wears a large Casio G-Shock GX-56-1B.

The only image we have so far is the one on the left, but the shape, size and details on the case of the watch show all the characteristics of this particular G-Shock. This immense watch is part of the extra large GX-56 series which features a new shock protection construction and tough solar (solar powered). 

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Casio’s newly developed double-layered urethane-resin bezel covers the case, button areas and watchband bindings with soft plastic, which is then overlaid with hard plastic. The watchband is connected to the case by screws to provide even greater reinforcement against shocks. Also available in black with black screen (GX-56-1A) and orange (GX-56-4). The watch with the light screen as seen in the film is currently not available on the USA website.