We claim the ornamental design for bar stool, as shown and described.
FIG. 1 is a front corner perspective view of a bar stool according to an embodiment of the invention. The view from the opposite back corner being identical to this view.
FIG. 2 is a side elevational view of a bar stool according to an embodiment of the invention. The view from each side being identical hereto; and,
FIG. 3 is a top plan view of a bar stool according to an embodiment of the invention.
The portions of the figures shown in dashed lines are for illustrative purposes only and form no part of the claimed invention.