We claim the ornamental design for a game board, as shown and described.
FIG. 1 is a perspective view of a game board, showing our new design;
FIG. 2 is a top plan view thereof; and,
FIG. 3 is a left-side elevational view thereof, the right-side elevational view, front elevational view, and rear elevational view all being mirror images thereof.
The broken lines in FIGS. 1 and 2 depict environmental matter and form no part of the claimed design. The constrasting shading represents contrasting colors. The bottom plan view does not form a part of the design.