Visa Mini
I carry a bundle of little barcoded store cards on a keychain in my pocket. Cards for area grocery stores, pharmacies, and other specialty stores. For me, the discounts outweigh privacy concerns. I also have a Mobil Speedpass on the same keychain, making it a snap to pay for gas or convenience store items. I never thought I'd see the day that I could put a credit card on that same chain.
Visa is introducing a mini version of their card in Australia and some asian markets. It makes a lot of sense. Gone are the days of manual imprints, so having large raised numbers is much less important. What really counts is the mag stripe on the back, and you don't need a full-size card for that. It can only be used in places where you manually swipe the card through a slot, but those readers are used in more than half the places I use my card, so it could be fun to try. They include a companion regular card that you can dig out when the mini won't work. Apparently Visa has distributed 11 million of these things in the U.S., but I have yet to see one.