Stalker: Call of Pripyat → Quests → One Shot
The mercenary leader and a certain "client" meet in the dorm courtyard. Our task is to take them both out with a sniper rifle. Sound familiar?
The Gauss is highly recommended for this mission, because even with the SVD, you'll have to take into account something as important as ballistics. Call of Pripyat handles them more than well, and if you aim for a mercenary's head with the SVD, the bullet will likely fly off in a completely realistic trajectory, leaving you simply spooking your targets. So, holster the SVD, pull out the Gauss, forget about ballistics, and fire.
Just don't shoot the first target right away; wait for the second one to arrive and for them to start talking. That Gauss thing is a cheat, to be sure...
Source: gamer.ru
See also:
Dungeon walkthrough (video)
Fallout Tactics: Medical supplies
Hydrocarbons - gas, oil, coal