The ornamental design for a bat, as shown and described.
FIG. 1 is a perspective view of a portion of a bat showing our new design;
FIG. 2 is a front view thereof, the rear view being a mirror image thereof; and,
FIG. 3 is a side view thereof, the opposite side view being a mirror image thereof.
The area within the solid and dash-dot dash lines forms the claimed design. The area within the broken lines is environmental and form no part of the claimed invention.