I agree with most of what ovis posted, especially after adding the 870. I would include the M70, also. Based on sales alone, I think it would be hard to dispute the Winchester 94 as the quintessential American long arm. Probably the 1911 Colt would be the handgun. Though the 1873 Colt SAA (Peacemaker) is uniquely American.

Let's not forget the M16 or AR15. The little black "evil" assault rifle is as American as mom's apple pie, as is the M1 and 14.

A lot of people make fun of the Winchester 94, but I don't think there is a better rifle for woodland/scrub/swamp deer hunting than the 94, especially chambered in the 30 WCF. Makes a nice little ranch rifle tucked in a scabbard for horse carry, too.