The ornamental design for a keyfob, as shown and described.
FIG. 1 is a top front perspective view of a keyfob showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top perspective view thereof; and,
FIG. 7 is a bottom perspective view thereof.
The broken lines represent portions of the keyfob that form no part of the claimed design. The shade lines in the drawings show contour and not surface ornamentation.