It probably depends on your generation. The first porn loop I ever saw was in 1973 with John Holmes and some hot brunette chick with big tits. I have always thought of Holmes and Ron Jeremy being the most famous but Peter North has probably been seen by more people.
My favorite of all time would be Christy Canyon. She was down here in the '80s in Ft. Lauderdale for an appearance at Pure Platinum. I will never forget meeting her in person. She wrapped her arms around me and blew in my ear whispering "Let's Fuck"....my dick got harder than Chinese arithmetic and I melted as she walked away looking over her shoulder and winked. She was hot!!