Here's one I had today, at imps:
What do you lead?
Say you lead the ♣A, and you see:
Partner plays the ♣Q and declarer follows.
Plan the defense.
The full deal:
I shifted to a diamond at trick two, killing the entry to the spades. Declarer won and took dummy's top hearts, but she couldn't cross to her hand to draw the last trump. She tried to cash the spades, but I ruffed the second round, and she went down. Continuing clubs also works, provided you knock out the ♦A next. A spade shift lets declarer take two rounds of trumps and ruff a spade high to cross back to hand.
Plus... it's free!