The best credit card or wallet knife ever, was the Microtech Option II, had one and carried for several years until my wallet was stolen out of my truck on Christmas Eve, nice huh. I only wish I would have caught em, I killed em all, miserably m#$#R F*(KRs, sorry I just despise thievery. Anyway it was a large frame lock folder that was very big but very easy to carry as a credit card at the same time, used it many times to clean squirrels, open feed bags and all kinda stuff. It was so big you could use it comfortably and it was big enough for real work and use.
The knife was awesome and then like everything that seems to be great it was in Mircotech infinite wisdom discontinued, I paid $80.00 for mine NIB. The sell on Ebay now for between $200.00 and $400.00 bucks.
Theres one up right now fleabay, I'd love to have it buy the econ is BAD, BAD, BAD down here and I'm broke as a joke.