Sure, some of that wallet bulge comes from old-fashioned cash, but let's face it, credit cards and receipts are the big contributors. With the One Card concept though, you'd have everything accessible by turning a knob on a single card.
Dreamed up by Kim Young Suk, the One Card is almost too great to ever actually become reality. It would come with a media card slot to add credit card information, a knob to select which card you want the magnetic strip to mimic, and a display which would show either the selected card or corresponding receipts.
Only trouble would be that you're kinda screwed if you manage to demagnetize the card somehow. [Yanko Design]