The ornamental design for a stylus, as shown and described.
FIG. 1 is a perspective view of a stylus showing my new design;
FIG. 2 is a front elevational view thereof; the rear elevational view being a mirror image thereof;
FIG. 3 is an enlarged left side elevational view thereof;
FIG. 4 is an enlarged right side elevational view thereof;
FIG. 5 is a top plan view thereof; the bottom plan view being the same as the top plan view; and,
FIG. 6 is an enlarged cross-sectional view thereof taken along the line 6-6 in FIG. 2.
The broken line showing is included for the purpose of illustrating portions of the article and forms no part of the claimed design. The dot-dashed lines show unclaimed boundaries.