The ornamental design for a hat, as shown and described.
FIG. 1 is a front perspective view of a hat showing my new design;
FIG. 2 is a front elevation view thereof; and,
FIG. 3 is a rear elevation view thereof.
The broken line showings of a hat in FIGS. 1, 2 and 3, respectively, are for the purpose of illustrating the environment in which the design is associated and form no part of the claimed design.