The ornamental design for a guitarendpin, as shown and described.
FIG. 1 is a front elevation view of a guitar end pin showing my new design, the rear elevation view being a mirror image;
FIG. 2 is a first side elevation view thereof, the second side being a mirror image;
FIG. 3 is a top plan view thereof; and,
FIG. 4 is a bottom plan view thereof.
The elevation view of the pin in FIG. 1 rotated 180° is the same as FIG. 1 and the elevation view of the pin in FIG. 2 rotated 180° is the same as FIG. 2.