The ornamental design for a wristwatch, as shown and described.
FIG. 1 is a front elevational view of a wrist watch showing my new design,
the broken line showing is for environmental purposes only and forms no
part of the claimed design;
FIG. 2 is a bottom plan view, the top being a mirror image thereof;
FIG. 3 is a left side elevational view; and
FIG. 4 is a right side elevational view thereof. The rear view, not shown,
is flat, plain, and unornamented.