I have Rainbow six Vegas 2.
You can snipe with a shotgun in that game.
As a matter of principle, I avoid the use of shotguns in multiplayer due to how annoying I find it to be killed by them.
Example of such annoyances is below, translated from xbox live language into proper English.
Guy with shotgun: Exuberance! I have killed you.
Me: Yes indeed my good man, however did you do it?
Guy with shotgun: Why good sir, I do believe that I used this shotgun to shoot your genitals at close range. Thus proving that I am superior in the field of digital battles.
Me: But good sir, you did not even aim your weapon. I feel that no skill was involved on your party and I am most indignant towards the foul tactics that you have employed.
Guy with shotgun: If that is truly the way you feel, then perhaps I shall make my character repeatedly crouch over the body of your fallen character. Signifying that I am partaking in a lewd act.
Me: How crude. I do not approve.
Guy with shotgun Further exuberance!
I prefer Sub Machine Guns, Assault Rifles and Light Machine guns.
Or swords.