Some of my favorites (others may occur later on):
The one I mentioned above, when Angelique’s curse to make Barnabas a vampire again comes up against Dr. Lang’s Mad Science skills to cure him, and Mad Science triumphs.
Quentin’s takeover of Collinwood.
Little ghost-Sarah telling her big brother Barnabas to behave himself.
Just after the end of 1790s storyline, Barnabas is convinced that Vicky must know his secret and so he bites her. Normally, when he bites people–Willie, Maggie, Carolyn–they have no will of their own. But Vicky wants to go look at the Collins family vault in the cemetery and see if the hidden room she remembers from the past is really there. Barnabas doesn’t want her to do that and tries to use his mind control on her. “You don’t want to go to the cemetery, Vicky.” And Vicky brushes this off; they’re going to cemetery, and she’s driving. You don’t usually think of her as strong-willed, but it made me wonder what he’d be letting himself in for if he did succeed in making her a vampire as he intended.
Back in the 1840 storyline, when Julia Hoffman is compelled to reattach Judah Zachary’s head to his body and reanimate him with lightning in a makeshift lab, with a faux-Cockney music-hall singer as her assistant. I know they were doing Zachary’s evil bidding, but I loved it.
The stiff competition between Crazy Future Carolyn and Crazy Future Quentin when Barnabas and Julia briefly visit the ruined Collinwood of 1995.
In 1897, when Quentin’s brother Carl tries to tell him that Barnabas is a vampire. Quentin laughs at this at first – “Our cousin Barnabas…” then his whole expression changes as he realizes Carl is right, “who we never see in the day time.”
The similar fates of the Witchfinder Trask and his grandson, the Reverend Trask. If my last name were Trask, I’d stay far, far away from any Collinses who looked like they were planning to do a little masonry work. Also related to this, the Witchfinder’s ghost having his revenge and holding a trial for Barnabas with his victims as the jury.
Julia Hoffman braining her evil alt-reality self with a poker.
When Elizabeth is about to blackmailed into marrying Jason McGuire and instead of saying “I do,” says “I murdered my husband, and that man helped me.” And then we find out what’s really in that locked room in the basement.
When Barnabas stakes Tom the vampire, since it strikes me as funny that the first person to stake a vampire on this show should be Barnabas.
When Charity/Pansy actually stakes Barnabas. I certainly wasn’t expecting that.