Daikokuten is a friendly god and his hammer is not a weapon like the Thor's hammer in the Norse mythology. The hammer of Daikokuten, called Uchide no Kozuchi, is a magical hammer that grants wishes and with a single hit it brings wealth and good fortune. That's why in Japan you may notice people carrying attached to their mobile phones small charms shaped like the hammer from this photo...
EXIF info:
Nikon D90
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 40mm
Aperture: F/5.6
Shutter Speed: 1/30s
ISO Sensitivity: ISO 500