Writing instrument

FIG. 1 is a front, right, and top perspective view of an ornamental design for a writing instrument according to the present invention;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof,

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and

FIG. 8 is a front, right, and top perspective view of an ornamental design for a second embodiment of a writing instrument according to the present invention, in which a barrel portion and front nose cone are translucent;

FIG. 9 is a front elevational view thereof;

FIG. 10 is a rear elevational view thereof;

FIG. 11 is a left side elevational view thereof;

FIG. 12 is a right side elevational view thereof;

FIG. 13 is a top plan view thereof;

FIG. 14 is a bottom plan view thereof;

FIG. 15 is a front, right, and top perspective view of an ornamental design for a third embodiment of a writing instrument with a translucent barrel portion, front nose cone, and grip according to the present invention;

FIG. 16 is a front elevational view thereof;

FIG. 17 is a rear elevation view thereof;

FIG. 18 is a left side elevational view thereof;

FIG. 19 is a right side elevational view thereof;

FIG. 20 is a top plan view thereof; and,

FIG. 21 is a bottom plan view thereof.

All portions shown in broken lines are environmental and illustrative only and form no part of the claimed design.