What's the most unusual thing you've received in the post?

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Some years ago, I sent my brother some of the most obscure general knowledge questions I could come up with. I sent them in the form of a competition and told him that certain items must be enclosed with his entry in order to qualify. I specified things like a blue elastic band, a used postage stamp etc and then added ' an unusual item of your choice'. Sure enough, I received his answers, the specified items and a match box containing his chosen item. It was the back end of a hornet with a label saying 'hornet's bum'. I still have it.