On the last level of 007: From Russia With Love, you have to destroy a plane, one of the enemies is in. It's parked at the end of the runway, firing rockets at you. You have a jetpack.
Now, there is a little alcove near the end of the runway, where the plane can't hit you, but you can shoot it just fine. Win, and continue with the level.
Also, in Stalker: Shadow of Chernobyl, during the first mission, you have to clear out a bandit camp. You can climb up into the 'attic', and there are 2 planks over a hole. Stand on them, and the bandits can't shoot you, but they will gather underneath you, and let you shoot them. Easy.
Note: Both of these I found after beating that part normally, (and painfully) many, many times.