Many games draw moral lines in bold colors, where the real world is not so easy to categorize. Suppose that the player characters are faced with an overwhelming foe? Even unsavory allies such as orcish barbarians may be better than no allies at all. More disturbing, these allies may be honestly friendly to the PCs when all is done, overcoming barriers of race and religion. Will the PCs remain friendly with the bloodthirsty humanoid tribesmen when their mutual foes are defeated? Some would expect the tribes to betray them, but after the characters have honestly won their respect, even orcs may not be all bad.
A girl living in an isolated hamlet is cursed: So beautiful and sweet-natured that no man can resist loving her, but she has never met the man she could love in return.
A powerful wizard that the PCs encounter is completely silent. He does not speak and cannot be heard as he moves. Even his spells are silent, but his magic is just as potent.
He has a tendency to summon invisible chairs, place foes in invisible boxes of force, and other "mime tricks".
The peasants of the wood use crudely carved symbols to ward off wolves. They think the symbols are emblems of purity and goodness and that keeps the wolves away. The symbols work, but not for the reasons the peasants believe...
The symbols are actually arcance evil symbols which the wolves know and fear, but to which the peasants are oblivious. So how gullible are the peasants going to be when a strange horned man displaying the symbols on his shield turns up and asks for their allegiance?