The ornamental design for a christmaslight, as shown and described.
FIG. 1 is a back perspective view of a Christmas light showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is a close-up view of the tip of one of the fiber optic cables showing the ornamental design in detail. The tips of each of the fiber optic cables are identical; and,
FIG. 7 is a close-up view of the tip of one of the fiber optic cables shown from the opposite side of FIG. 6.
The broken line showing of the electrical wires is included for the purpose of illustrating environmental structure and forms no part of the claimed design.