M1 Garand
Underrated:
The M1 Garand is a great gun, definitely underrated. It has a lot of power and range, and other than the unusual magazine design, it is one of the best guns ever made. I am the proud owner of two. My unmodified one can get a 4in. pattern at 800yds, which is pretty good, considering the gun is over fifty years old. My modified one can get a 1in. pattern at 800 yds. It has been modified heavily, and when loaded with handloads, is probably my most accurate and powerful rifle.
Overrated:
The M-16 is a good gun, but the government has ruined it. It fires wimpy bullets, so you need a burst or autofire option to get guaranteed kills. It doesn't have enough range or accuracy to ever be more than a military assault rifle. Finally, the government has been stupid enough to change the gun. All new M-16s have lost the ability to go full auto. Without that factor, the gun becomes almost worthless as a military rifle. In combat, a FN FAL would be more reliable, and would have a better chance of one-shot stops.