I claim the ornamental design for a flashlight, as shown and described.
FIG. 1 is a perspective view of a flashlight according to my new design;
FIG. 2 is a left side elevation view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a front elevation view thereof; and,
FIG. 6 is a rear elevation view thereof.
Broken lines immediately adjacent shaded areas represent bounds of the claimed design. All other broken lines are directed to unclaimed features. The broken lines form no part of the claimed design.