Well let's break that name down. 'Ultra' is Olde English for 'helluva' and 'gunner' actually comes from ancient Egyptian texts originally, always in refence to the armed guards the aliens who built the pyramids used. The hieroglyph for it interestingly is remarkably similar to a Thompson submachine gun. So from the name we get that the Ultragunner is 'helluva' and is in some way connected with a Tommy gun. When I think 'helluva' and a Tommy gun I think Al Capone, thus logically the Ultragunner is a giant robot Al Capone armed with the signature mob weapon of his era.