The ornamental design for a massagegun, as shown and described.
FIG. 1 is a perspective view of a massage gun showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a right side view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines that are immediately adjacent to the shaded areas and define unshaded regions depict the bounds of the claimed design. The broken lines that are shown within the broken line boundaries indicate portions of the article that form no part of the claim. The broken lines themselves form no part of the claimed design.