The ornamental design for a impact wrench, as shown and described.
FIG. 1 is a left side view of an impact wrench showing my new design; the right side view being a mirror image;
FIG. 2 is a rear view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a left side perspective view thereof; the right side perspective view being a mirror image;
FIG. 7 is a top perspective view thereof; and,
FIG. 8 is a bottom perspective view thereof.
The broken line showing is for illustrative purposes only and forms no part of the claimed design.