The ornamental design for a corkscrew, as shown and described.
FIG. 1 is a front top perspective view of the corkscrew showing my new design.
FIG. 2 is front bottom perspective view thereof.
FIG. 3 is a side view thereof where the corkscrew is tilted so that the top portion is further away than the bottom portion.
FIG. 4 is side view thereof.
FIG. 5 is another side view thereof.
FIG. 6 is a back view thereof.
FIG. 7 is a front view thereof.
FIG. 8 is top view thereof.
FIG. 9 is a bottom view thereof.
FIG. 10 is a view thereof where the top portion has been extended and placed in an open position; and,
FIG. 11 is a side view thereof where the corkscrew is tilted so that the top portion is further away than the bottom portion and wherein the top portion is in an open position.
The broken lines in the drawings illustrate portions of the corkscrew which form no part of the claimed design.