In Sniper Elite V2 for the PC, PS3, and Xbox 360, you can tag enemies to mark them for your teammates.
In order to tag an enemy, you have to be on a difficult lower than Sniper Elite, and you have to be using the binoculars. Hover over an enemy with the binoculars and click down on the left stick.
There should be a button mapped for tagging on the PC, so please post a comment if you know what the default is.
