The ornamental design for a finial, as shown and described.
FIG. 1 is a perspective view from below of a finial in accordance with my design;
FIG. 2 is an enlarged perspective view from below of the finial in accordance with my design;
FIG. 3 is an enlarged bottom plan view of the finial in accordance with my design; and,
FIG. 4 is an enlarged side elevation view of the finial in accordance with my design, all sides being substantially identical to that shown.
The broken line showing of the ceiling fan is included for the purpose of illustrating environmental structure and forms no part of the claimed design.