If you were standing in front of a door, one leading to heaven and one leading to hell, neither of which are labeled, and guarding that door is a guard, one who always lies and one who always tells the truth, but you don't know who's who, what question would you ask to definitively know which one is the door to heaven versus hell.\nanswer: "what would the other guard say that you would say is the door to heaven (hell)?" then you know the opposite door is the door to heaven (hell)
What is the best riddle that you know?