Sniper Elite 4

You'll probably get this without knowing. Snipers aren't that hard to see in the game with their glowing glint from the scope in the distance, you also get a sound warning like a ding to warn you there is one in the area. Provided the sight bar is empty or yellow, it will count. If the player sighted bar turns to red either restart the checkpoint or carry on due to there being plenty of snipers about. Killing snipers will sometimes be part of some secondary objectives as well.