Place Dun Dun Dun just before the twist is shown, put this clip on the reveal itself, then follow it with Vine Boom for impact and Anime Wow for a second reaction.
About this sound
This clip is a single drawn-out woah, held for almost six seconds while the speaker stretches the word as if they cannot quite believe what just happened. It feels amazed, stunned and a little playful, the kind of reaction that makes a surprising moment feel bigger and funnier to everyone hearing it.