We claim the ornamental design for an electric grease gun, as shown.
FIG. 1 is a perspective view of an electric grease gun showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a rear elevational view thereof;
FIG. 7 is a front elevational view thereof; and,
FIG. 8 is another front elevational view of the electric grease gun, shown without the cylinder and hose.
The cylinder and hose are shown in broken line form since they depict portions of the electric grease gun in which the design is embodied that are not considered part of the claimed design.