When I think of someone playing the bodyguard gimmick in wrestling, I think of someone that looks like he's able to kick somebody's ass and is able to follow through if necessary. I also look at it, ideally, as a means of potentially elevating someone, giving them an opportunity to establish a presence with the audience in the arenas and on TV at home.
When it came to someone who generally looked the part the best, I mean in terms of someone who seemed to dress & behave like a "real bodyguard", was probably Rick Rude. It came about late in his career and while I found him infinitely more entertaining in his "Ravishing" days, he was still able to effectively sell himself as someone you didn't wanna screw with. He had the suit, he had the presence, the way he carried himself, the beard and that sense of seriousness & stoicism. Unfortunately, by the time this came along, Rude was in both the final period of his career and life.
Chyna would have to be considered one of the overall top ones. Even though Chyna was female, she was the kind of female that definitely stood out. During her very first appearance, when she was swinging Marlena around like a ragdoll, I thought it was a guy for a few minutes. She certainly had the physical build of a man and that square, masculine looking jawline reinforced the notion. It was unusual to see a woman in that role, plus it added a new element to the gimmick: what are you supposed to do when the bodyguard is a woman and you're raised in a society where physical violence towards women is vehemently looked down upon? She also had that sense of stoicism and seriousness about her much of the time. While HBK & Triple H were running around like a couple of frat boys on horse crank, she'd stand there with her arms crossed looking out over the crowd as if looking for trouble.
Diesel would probably have to be viewed as another of the best, at least in my view. He started out as the bodyguard but it grew from that into he & Shawn being buddies rather than "employer and employee." Diesel, AKA Kevin Nash, was in his mid 30s, legitimately close to 7'0", maybe a little over or right around the 300 lb. mark so he definitely had the look and intimidation factor going for him.