SPOILERS!!!!
Most memorable would have to be the scene in 1970PT, when twin sisters Angelique and Alexis traded places, against Alexis' will. When Alexis went to say goodbye to her supposedly dead sister, Angelique, and reached out to touch her, the latter opened her eyes and informed her terrified twin that she was going to take her place. Angelique killed Alexis, placed her in the coffin in which she had been resting for six months, took her place at Collinwood and stole her sister's life, her intention to get revenge on Quentin for killing her (he hadn't, but she didn't know that). In a very tricky split screen, rarely done in soaps at the time, we saw Alexis and Angelique together, a special effect skillfully done--and very scary!
Least memorable? Probably Philip Todd's, mainly because I can't seem to remember it!
Love, Robin