I thought Frank DeFeo was really hot. He never really went all the way, but did a lot of muscle worship films, and seemed to be inching towards gay sex, even though he was gay-for-pay. It's a shame he died so young.
Another favorite was the guy who started on Active Duty as Shawn, but he really bulked up and became a muscle stud under a different name. I think he got into some trouble , since I seem to remember him making an appearance on Porn Star Mug Shots. But I'll always remember him in a scene with Damien on AD.