The queen trap out of the Fort Knox variation of the French Defense can catch even a Grandmaster opponent. It's a very instructive trap since from the variation itself, one learns about a strategical concept. Moreover, the trap highlights many important ideas in chess. Namely, the importance of move order, why it's not a good idea to bring the queen out early, and accurate calculation. Lastly, do not underestimate the power of in-between moves (zwischenzug), and discovered attacks.
http://www.youtube.com/watch?v=Z3R1Z0dPWww