The ornamental design for a tweezer, as shown and described.
FIG. 1 is a front view of a tweezer showing one embodiment of my new design;
FIG. 2 is a plan view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof; and,
FIG. 5 is a front view showing the tweezers closed.
The rear view and front view, and the bottom view and plan view are respectively symmetrical to each other, and thus the rear view and bottom view are omitted. The broken lines immediately adjacent the shaded areas represent the bounds of the claim and all other broken lines are for illustrative purposes only. None of the broken lines form a part of the claimed design.