The ornamental design for a flashlight, as shown and described.
FIG. 1 is a perspective view as viewed from a front direction of a flashlight showing my new design;
FIG. 2 is a top side view thereof;
FIG. 3 is a bottom side view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a right side view thereof; and,
FIG. 7 is a left side view thereof.
The broken line showing of strap is included for the purpose of illustrating the strap is broken away to indicate indeterminate length and forms no part of the claimed design.