The ornamental design for a billiardcue, as shown and described.
FIG. 1 is a right side view of a billiard cue design.
FIG. 2 is a top view thereof.
FIG. 3 is a left side view thereof.
FIG. 4 is a bottom view thereof.
FIG. 5 is a reduced top view thereof, the broken line showing of the forward portion of the billiard cue is for illustrative purposes only and forms no part of the claimed design; and,