The ornamental design for golf ball marker, as shown and described.
FIG. 1 is a bottom perspective view of a golf ball marker in accordance with the new design;
FIG. 2 is a top perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken lines shown in FIGS. 1-6 are directed to environment and are for illustrative purposes only; the broken lines form no part of the claimed design.