It's a boringly popular answer, but for me it's the honest answer.... Ginger Lynn.
She was a spellbinding performer. Watching some of her scenes, I really don't understand how the guys managed to contain their loads, a lot of the time. More than most performers since and all the performers of today, when I watch certain things she did and the way she did them, I think "I wouldn't be able to cope with that, I'd be going off already."