Dishonored has some fun moments like these. In the first mission, you're given an optional objective to save a guard officer from your target, who plans on poisoning him. If you break the bottle of poisoned wine, the target will lead the guard to his personal quarters to grab another bottle, as well as to show off the painting you mentioned in your post. Now, the guard will attack you anytime before then. However, if you follow them to the the target's quarters, and wait until he draws his sword to attack the guard before killing him, the guard will blink in confusion, thank you for saving his life, and flee the area, completing the objective.
Later, there's a level where you sneak through a base full of assassins. You come across a reference to the original Thief, in the form of an obstical course being run by a recruit. If you take out the assassin assessing the recruit and drag him off, when the recruit comes back to the starting position, he'll look around, crouch down, draw his word, and start searching the area.