A big black sharpie marker.

My name is on the front of one, and it says "Dad's" on the front of the other.
I keep the cards together, but keep all the ECBs and CRTs in separate slots in my CVS coupon organizer.
A benefit of having the names on the front is that when I do two separate transactions I can make it obvious to the cashier that they are separate cards - if I want to.
For me that's good, I only have 2 stores I can go to (and I mostly go to one) - so it's easier when they know (think) I'm doing the deals for someone else too. Funny how I do *all* his CVS shopping... though I do drag him in there every couple of months or so. Well, okay, only when they have a 'senior' coupon. lol
ETA: Just noticed that you said 'multiple cards in your name'... My answer is still the same actually... if my dad didn't live in town I'd probably still have 'his' card. You know, for all the stuff I bought for him, to send to him for Christmas or something. If I got another card in my name I'd still mark them on the card somehow - maybe with a small colored dot sticker? (Love the colored envelopes idea above!)