For no reason in particular other than my own interest, I need to know what the perfect "survival card(s)" would be.

What tools would you be very fucked to be without, &/or would want an excess of during a survival situation?
They have to be the to be the length, width, and general thickness of a standard credit card though; needs to fit in a wallet.

A magnifying lens card is of course a given (same with a tick remover), but what would be useful on a laser-cut metal card?
Would a saw be useful? I see other sets with snares, but I don't feel like a fishing kit would be too useful.