The ornamental design for a pipettetipbucket, as shown and described.
FIG. 1 is a perspective view of a pipette tip bucket showing our new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a back elevational view thereof;
FIG. 4 is a side elevational view thereof;
FIG. 5 is an opposite side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dashed lines immediately adjacent to the claimed areas in FIGS. 1, 6 and 7 represent the boundaries of the claimed design and form no part of the claimed design.