I also find this weapon very useful against the tougher enemies. He meant the 'Terrible Shotgun', which is found from the merchant 'Smiling Jack' in Evergreen Mills. Just wait until you have to go into their sanctuary for the bobblehead. You find them with the enclave and in the north west of the wasteland. I can take one out with about 3 head shots with the terrible rifle (a unique combat shotgun). It depends on what lever you are and your skills.
