The ornamental design for a handtiller, as shown and described.
FIG. 1 is a perspective view of a hand tiller showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left elevational view thereof;
FIG. 5 is a right elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is an enlarged view of portion 8 shown FIG. 2.
The dashed or broken lines shown in the drawings depict portions of the hand tiller in which the design is embodied that form no part of the claimed design.