One of my favorite tricks is to throw them into the microwave for a few seconds. This causes the shiny data side to get this cool rectangular crackle pattern. then you can use them for any of the above projects. also, you can glue 5 of them together shiny/crackly side out to form an open-topped box for business cards, post cards, etc. You just have to watch out for the open corners.
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You know, just once I'd like to meet an alien menace that wasn't immune to bullets. - Lethbridge-Stewart, (Doctor Who TV series)