The ornamental design for a massageball, as shown and described.
FIG. 1 is a front, right, and top perspective view of a massage ball, showing my design.
FIG. 2 is a rear, left, and bottom perspective view thereof.
FIG. 3 is a front elevation view thereof.
FIG. 4 is a rear elevation view thereof.
FIG. 5 is a left side elevation view thereof.
FIG. 6 is a right side elevation view thereof.
FIG. 7 is a top plan view thereof.
FIG. 8 is a bottom plan view thereof.
FIG. 9 is a partial enlarged view of an area labeled 9 in FIG. 2 comprising a side wall; and,
FIG. 10 is an exploded view thereof.
The broken lines shown in the drawings are included for the purpose of illustrating portions of the massage ball that form no part of the claimed design.