The ornamental design for a gunholster, as shown and described.
FIG. 1 is a perspective view of a gun holster showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is a perspective view of the gun holster where the gun holster is in a configuration of use.
The broken lines in the drawings depict portions of the gun holster, and additional environment matter in FIG. 9, that form no part of the claimed design.