FIG. 1 is a perspective view of a first embodiment of the writing instrument;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a front view thereof; and

FIG. 7 is a rear view thereof.

FIG. 8 is a perspective view of a second embodiment of the writing instrument;

FIG. 9 is a top view thereof;

FIG. 10 is a bottom view thereof;

FIG. 11 a right side view thereof;

FIG. 12 is a left side view thereof;

FIG. 13 is a front view thereof; and

FIG. 14 is a rear view thereof.

FIG. 15 is a perspective view of a third embodiment of the writing instrument;

FIG. 16 is a top view thereof;

FIG. 17 is a bottom view thereof;

FIG. 18 is a right side view thereof;

FIG. 19 is a left side view thereof;

FIG. 20 is a front view thereof; and,

FIG. 21 is a rear view thereof.

The stippling represents a contrast of color. The broken lines in the drawings showing the lead and lead guide, anterior openings, and mold injection point form no part of the claimed design. Additionally, the broken lines immediately adjacent the shaded areas in FIGS. 2, 5, 9, 12, 16, and 19 represent the bounds of the claimed design and form no part of the claimed design.