The ornamental design for a plunger, as shown and described.
FIG. 1 is a diagrammatic perspective view of the plunger in full lines with
a drain and hands shown in broken lines representing environmental
association matter being for illustrative purposes only and forming no
part of the claimed invention.
FIG. 2 is a front elevational view thereof, the rear, left and right side
elevational views being mirror images of the front view;