The most popular G.I. Joe: A Real American Hero character is Snake Eyes. He was part of the original 1982 straight arm 3.75 inch release. I have the 1983 swivel arm battle grip version and I do not have either of the two original accessories that came with the figure- an explosives pack and a UZI sub-machine gun.
Snake Eyes is classified as an Army Commando on the original release and readers of the Marvel Comic G.I. Joe: A Real American Hero got to go far more in-depth with the character than the file card. Snake Eyes was originally a Vietnam L.A.R.P. trooper in the same unit as Stalker and Storm Shadow. Later in the Marvel Comic run the ninja aspect of the character was added but in 1982-83 Snake Eyes was simply a Commando with an extensive martial arts background. He was also really cool decked out entirely in black.
Snake Eyes, like Stalker, is one of the only first wave of G.I. Joe figures with an original head sculpt not used on any other figure. His other body parts were used on other figures in the wave but not the head. He also did not come with a backpack.