The ornamental design for a hardhat, as shown and described.
FIG. 1 is a rear perspective view of a hard hat showing my new design;
FIG. 2 is a right side elevation view thereof, the left side being a mirror image;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a front elevation view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a rear perspective view of a second embodiment thereof;
FIG. 7 is a right side elevation view of FIG. 6; the left side being a mirror image;
FIG. 8 is a rear elevation view of FIG. 6;
FIG. 9 is a front elevation view of FIG. 6; and,
FIG. 10 is a top plan view of FIG. 6.
The details shown in broken lines form no part of the claimed invention. The shaded portions of the brim in FIGS. 6-10 represent a different material from the remainder of the hard hat.