American Express just introduced their new Butterfly Card, a foldable card and keychain carrier available to all of their Gold Card holders.
Similar to the Discover 2GO Card, the concept is to make taking (and therefore using) your card as convenient as possible. Since most people use some sort of key chain it's a logical choice to design around.
The card can be handled like a standard card, left halfway in the case with the magnetic strip exposed, or folded up in the case and slipped easily in your pocket, purse or on your key chain.
Also on CH: American Express Red Card
via JK On the Run