Method: When the matches come into contact, Brian flicks the end of one match which then propels the other into the air.
Need: The key to making this effect work is I BUILD ANTICIPATION. If you just walk up to someone and flick the match, nobody will be impressed. But if you carefully position the first match in their hand, then make a production of shuffling around to build up static electricity, the anticipation of something dangerous about to happen will put the mark on edge. It's that tension that gets turned into a yelp when the match rockets up into the air.
Bonus: when you flick the match, it makes a crackling sound that sounds like a spark!