The ornamental design for a shower head, as shown and described.
1. Shower head
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
Materials include metal and synthetic resin; the claimed design is for a shower head which is used with a hose; fig. 1.1 is a front perspective view of a showerhead; fig. 1.2 is a front elevational view of the showerhead shown in fig. 1.1; fig. 1.3 is a rear elevational view thereof; fig. 1.4 is a left side view thereof; fig. 1.5 is a right side view thereof; fig. 1.6 is a top view thereof; fig. 1.7 is a bottom view thereof; the dotted lines of figs. 1.1 and 1.2 are for illustrating nozzles of the shower head; thin shading lines are only to show the contour of flat and curved surfaces and form no part of the claimed design. The broken lines in the drawings illustrate portions of the shower head which form no part of the claimed design.