Citi DoubleCash, it started its life as a Diamond Preferred back in 2011.
I went through a tough time a few years ago, and lost all my credit cards except for that one, which I intentionally kept current so that I wouldn't have to completely start over from scratch. Glad I made that choice.
My first ever credit card was a Providian, circa ~2001. They later became WaMu, and then Chase... marking the first of 3 or 4 Chase credit cards I've stupidly burned over the years. Why they gave me 2 more recently, I have no idea.
Total Loan Balance: $43k / $65k
Total SL: $78k
My Discover, which will be 10 yo later this year.
Then there is my husband's Citi Costco, dated from year 2000, when he was 8 years old. Thanks to the amazing back dating of Costco Amex. 
I am kicking myself for totally missing that train. My parents had Amex dated from the 80's and I could have easily hopped on.
I promised DH, 1, I shall never divorce him and 2, we shall never quit Costco. 
Nordstrom store card, opened on May 1992 while I was waiting tables and going to school. This was my second department store card, and the SL was $600.
