Alabasta is what got me hooked, but it was scenes from Thriller Bark, Impel Down and Marineford from the One Piece in 6 Minutes AMV, as well as the Zoro's sacrifice video, that spurred me to continue reading the series(I had stopped around the middle of Arlong Park at the time).
The start of the series I loved it, love Pirate stories. Thriller Bark was alittle boring for my taste during a second watch through so I skipped it until the end.