I probably heard "Hound Dog" first (my father was a BIG Elvis fan), but the one that really took my fancy was "Jailhouse Rock."
You see, the school where I took dance lessons used a pianist for most of the accompaniment, but every so often, a pop song would catch my teacher's fancy, and we'd have a number choreographed to it. "Jailhouse Rock" and "Mack the Knife" were the first two 45s I remember my teacher using as accompaniment for routines. We also did "Harlem Nocturne" and "Quiet Village" during those years, as I recall. I loved all of them.
I took dance lessons there (tap, jazz) for ten years, and by the last few years, the piano had been moved out of the studio, and we had gone completely to records and tape.