Tom Clancy's Rainbow Six Vegas 2 Tips
Load up a T-Hunt on the CBQ Training level. Do it by yourself; don't take teammates. Make sure you equip the first sniper rifle, SR-25. The is a necessity because the sniper is silenced. You will spawn in one of the buildings. Walk out door infront of you and go left a bit and there is a small dead end. (NOTE: Don't go in the next building) Now turn around and you should see three guys all the way down the path. Snipe them all. It doesn't half to be a head shot because regardless you will get 'Kill from Long Range.' Now, depending on the spawn of the map, three to four other terrorists will walk out and you can snipe them too. Rinse and repeat and you will get 20 Marksman in no time.