I claim the ornamental design for a sharpener/eraser, as shown and described.
FIG. 1 is a front view of the sharpener/eraser.
FIG. 2 is a rear view thereof;
FIG. 3 is a right side exploded view thereof;
FIG. 4 is a right side view thereof, wherein the left side view would be a mirror image thereof, the top view would be identical thereto, and the bottom view would be a mirror image thereof;
FIG. 5 is a rear/right/top perspective view thereof; and,
FIG. 6 is a front/left/top perspective view thereof, wherein the front/right/top perspective view the front/right/bottom perspective view, and the front/left/bottom perspective view would all be mirror images thereof.
The dash-dot lines represent the bounds of the claimed design, while all other broken lines are directed to environment and are for illustrative purposes only; the dash-dot lines and the broken lines form no part of the claimed design.