Fruit, Money, and Laser Tattooing
The best I ever find is phone numbers and grocery lists...
Collectors Go Bananas For Flawed $20 Bill (CNN.com)
Apparently I missed this when it first appeared in 2003 on eBay. At one point I thought about about collecting those little stickers. But then I realized I already have enough dorky hobbies.
This reminded me of another article I saw a while back...apparently those stickers may be on their way to becoming things of the past. So maybe I should start collecting while I still can.