The ornamental design for a flashlight, as shown and described.
FIG. 1 is a perspective view of a flashlight;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line showing of the flashlight are environmental and form no part of the claimed design. The broken line showing of the symbolic break forms no part of the claimed design. The appearance of the article between the break lines forms no part of the claimed design.