CardSharp Credit Card Knife from Iain Sinclair

The CardSharp utilizes a creative and unique folding method to allow the knife to maintain a much smaller profile. This pocket knife easily fits into the same space as a couple of credit cards. The secret is the almost-one-piece design; the knife lacks the liners and pins that add to the thickness and weight of a normal pocket knife. Additionally, once fully deployed, there are no concerns about the knife closing when you do not want it to — via Knife Center