If you watch the following video, you will be able to see one of the world's leading card-throwing experts practicing his craft. With a business card and a flick of his wrist he can pop balloons, extinguish candles, hit targets, etc.:
Around the 50-second point, you will also see him impale a tomato with a business card. This is where the lethality comes in. The art of deadly card throwing was first popularized (as far as I know) by a performer named Gallagher, who could dismantle a watermelon with playing cards. In the following video you can see Rick Smith, the world record holder for card throwing distance, showing how to dismantle a banana around 2:00:
Around 3:15, Rick Smith demonstrates his technique very quickly. If you would like to learn to throw lethal playing cards yourself, the following video goes into more detail:
If you need a source of cheap playing cards, check out the dollar store - two decks for a buck.
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