I came up with an English puzzle, for the high school game I talked about yesterday.
It's a logic puzzle, where the goal is to find Shakespeare's twelfth play. You get a list of Shakespeare's plays, and a bunch of clues to help you put them in chronological order. The clues are things like "Romeo and Juliet comes before Hamlet". Since he worked on forty or so plays, this would be a somewhat long puzzle with many clues.
The twist to the puzzle is that everything is a red herring, and the correct solution is The Twelfth Night. Get it? That is Shakespeare's "twelfth" play!
I eventually decided against using the puzzle in the game, because I wasn't sure people could figure it out. I know if I encountered a puzzle like that in a game, I'd feel cheated or tricked. Plus, it'd take a long time for me to come up with a list of clues for sorting Shakespeare's plays. So I ended up having the game gloss over the puzzle, with someone describing the trick puzzle solution in passing.