The ornamental design for a flashlight, as shown and described.
FIG. 1 is a perspective view of a flashlight according to our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is back elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a top side elevation view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dash-dash broken lines show unclaimed portions of the flashlight and form no part of the claimed design, while the dash-dot-dash broken lines represent a boundary of the claimed surface.