Does anyone knows if every SmartCard has some unique identifying number that can be read by using ordinary card reader?

Number format doesn't matter at all (or string format), just the fact that it exists and that it's readable is enough.

I know that new smartcards can be programmed to my liking, and that I can issue unique IDs to them in the process, but I'm more interested in reading unique ID from credit cards, phone calling cards, stuff like that.

I should probably mention what is intended purpose for this, before I get incinerated. I want to find easy way to uniquely identify walk-in customers, most of people have at least one smartcard in their pocket...