The Stafford Gambit
Black to move. Mate in 1.
Snort took your queen, and his king stepped out. Mate him.
Hint
White's king is out in the open. Check it from far away.
Answer
Bg4# — Checkmate! You gave the queen and still won.
The idea
A king that walks out early is easy to hunt. Long-range pieces check from far away.
This chess trap is one of 30 quick puzzles in the Chess in 40 Seconds trainer: find the move on the board, get a hint if you're stuck, and learn the idea so you never fall for it in your own games.