It seems to me that a common misconception is that a marksman is the same as a sniper, and vice-versa. Not trying to flame anyone, just putting in my two sense. Both are equally important, I just want to see who agres with me.
A sniper. Ah yes. Every HVT's worst nightmare, and a very valuable combat asset, in terms of recon and selected elimination. A sniper is a very valuable asset to the team when little is known about the enemies approach or concentration.
A marksman, though similar, does have it's differences. I myself have had experience as a marksman, and my role was to provide medium to long range (via scoped sniper rifle), accurate and dealy covering fire for the rest of my squad. Moving with that frontline squad, and participating in ANY maneuvers.
I feel that the only real difference between a marksman and sniper is how you choose to employ your skills.