The ornamental design for a gametablet, as shown and described.
FIG. 1 is a top, front, right side perspective view of the game tablet;
FIG. 2 is a top plan view;
FIG. 3 is a bottom plan view;
FIG. 4 is a front elevational view;
FIG. 5 is a rear elevational view;
FIG. 6 is a left side elevational view; and,
FIG. 7 is a right side elevational view thereof.
The broken lines adjacent to the surface shading define the boundary of the claimed design. Other broken lines are included to illustrate portions of the design not claimed. None of the broken lines form part of the claimed design.