The ornamental design for a cap opener, as shown and described.
FIG. 1 is a rear perspective view of the cap opener showing my new design;
FIG. 2 is a cross section view taken along line 2--2 in FIG. 1;
FIG. 3 is a front perspective view thereof engaged with a pull ring of a can. The broken lines showing a portion of a beverage can is for illustrative purposes only and forms no part of the claimed design; and,
FIG. 4 is a partial view of the cap opener engaged to a bottle cap pull tab.
The broken lines showing a top portion of a bottle is for illustrative purposes only and forms no part of the claimed design.