All the needed cards ....
A bank card (any expense, even newspapers or bread).
My belgian ID card (with a chip)
My driver's license(11 languages).
A blood card (A+).
My SIS card (to get medication, to be allowed in the hospital..).
My VISA card...
Perhaps, one day, the ID, the SIS and the driver's license will merge..
I had a US social security card when I was a US citizen (not larger than a stamp) (with written on it: "not valid for employment") but lost it years ago.