I claim the ornamental design for an oyster shucking knife, as shown and described.
FIG. 1 is a top plan view of a handle and blade for an oyster shucking knife, wherein the bottom plan view (not shown) is a mirror image of the top plan view FIG. 1 of my design;
FIG. 2 is a right side elevation view, wherein the left side elevation view (not shown) is a mirror image of the right side elevation view FIG. 2;
FIG. 3 is a front elevation view of my design; and,