Excellent question, Lindsey!
Joan Bennet: Definitely Judith Collins! She was a strong and intelligent character with a mind and a will of her own that even Grandmamamama Edith seemed to recognize when she made Judith the head of the household, a role in which she proved extremely capable. Judith was able to keep her brothers in check and overcome various other obstacles, such as the insanity induced by Evan's black magic. Though she did make a terrible error in judgement with Gregory, she knew how to correct her mistake...
John Karlen: This is probably the hardest one to answer, but I'll have to go with Willie. I adore all of John Karlen's characters. Each was so likeable and well-acted: playful Carl, tragic William H. Loomis, heroic Kendrick and Desmond. However, when I began to watch the show, Willie Loomis was the first to catch my attention. He was the perpetual underdog; basically good, struggling to do his best, and harassed at every turn. Who couldn't help but like him?
Nancy Barrett: Charity Trask/Pansy Faye was wonderful to watch, but I think Barrett gave her best performance as crazed Carolyn Fredericks in 1995. This demented, wild-eyed, sometimes childlike character was worlds away from the Carolyn of 1970 or even 1966, and she helped to make it conceivable that something incredibly traumatic had occurred.
Louis Edmonds: It's a tie between PT Roger and Joshua. Joshua was a very complex, conflicted character, one that I appreciated more with a second viewing. However, parallel Roger was such a cold SOB, and he seemed so different from Edmonds's other characters. When I watched 1970PT, I hadn't yet seen early Roger, but even he could at least be charming when he wished. His alter ego had nothing to redeem him.
Thayer David: Another difficult choice. I think he did his best work as Ben, but he was so natural in the role of the professor. Really, I think Professor Stokes was one of the most consistent, believable characters of the show's entire run. He was strong-willed, brilliant, bold, sarcastic, cultured, courageous, helpful, patient, and discreet. Stokes was the one who always had to solve everybody's problems and clean up after Barnabas and Julia. As I've posted in the past, he was called upon to do some pretty remarkable things, and even though he probably should have told certain people to go jump from Widows' Hill, he always came through.
KLS: I'd have to say early Maggie. She had wit and personality and seemed like a nice, normal person. About the time of the Adam storyline, unfortunately, her character began to degenerate.
Grayson Hall: I do like Countess Natalie and Magda, but I think my favorite Hall character is PT Hoffman. As with Roger, she was so much colder and more menacing than the Julia we had come to know. While Hoffman the doctor was often in hysterics, Hoffman the housekeeper was practically emotionless, and I was impressed by how much Hall was able to control her mannerisms.
ProfStokes