We claim the ornamental design for a megaphone, as shown and described.
FIG. 1 is a perspective view of a megaphone of the present invention;
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 lines shown represent unclaimed subject matter and form no part of the claimed design. The dot-dash broken lines immediately adjacent to the claimed areas in the views represent the boundaries of the design and form no part thereof.
None of the broken lines form any part of the claimed design.