When Buffy slays the first member of the Order of Taraka, she supposedly slits his throat, but absolutely no blood was shown during or after his death to keep the show from being censored.
As Buffy is telling the vampire Dalton "...you're not a people.", she is looking directly at him while saying it as he stands in front of the mausoleum door. As she turns around, the camera points directly at the door and Dalton is suddenly gone.
One of the assassins of the Order of Taraka is shown getting off a bus. In a wide shot, the steps are one color with signs reading "Watch your step". In the close up, the steps change color and the signs are missing.
Willow explains to Giles that she is afraid of frogs, but in Inca Mummy Girl (1997) she is seen playing with a stuffed plush frog. Of course, this isn't a real frog. Willow isn't afraid of toy frogs.
When Angel is in Buffy's room, he walks by a mirror and we can see his reflection.
The first attacker of the Order of Taraka, drops 'dead' on the ice, but when Angel inspects the attacker's ring, you can clearly see him breathing.
At twenty-one minutes in, as Giles talks to Buffy outside the du Lac crypt and starts to walk away, you can see a crew member moving around behind the shrubbery at the left edge of the picture.
After killing the would be assassin on the ice, Angel has his vampire face. The way he talks to Buffy makes it seem that he has no control over when his face will change back by saying she shouldn't have to touch him when he's vampirish. But other times, with him and other vampires, they can change to and from their vampire selves at will.