I claim the ornamental design for a facial exercise device, as shown and described.
FIG. 1 is a top right perspective view of a facial exercise device in the extended position, showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a side elevational view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a rear elevational view thereof; and,
FIG. 6 is a front elevational view thereof.
The broken line showing of a facial exercise device is for the purpose of illustrating portions of the article that form no part of the claimed design.