I'll go with the 480 Ruger. A handgun cartridge that offers 30% more frontal area and bullet weight than the 44 mag in a factory revolver that is still packable and shootable by mortals w/o resorting to a muzzle break.
Can't think of a rifle cartridge developed in the past 20 years that can do something that hasn't been done by those in the prior 50 years.
