Inspired by @gwcoffey UPDATE: I switched my answers because fuck it guys I love apparition so much sorry not sorry
  1. Apparition lessons in the great hall
    Still bitter this didn't make it into the movies
  2. Honorable mention: When Harry and Voldemort's wands connect for the first time and priori incantatem brings out his parents, Cedric, etc help him escape the graveyard.
    We realize how strong their connection is here and set the tone for the remainder of the series. I remember being completely enthralled at this part of the book.