stupefier
/ˈstupəˌfaɪər/
noun
- Something or someone that causes extreme surprise, shock, or confusion.
- The magician's final trick was a stupefier that left the entire audience speechless.
- That math problem was a stupefier; even the teacher had to check the answer twice.
- The final plot twist in the movie was a real stupefier — nobody saw it coming.