Lord of the Rings fall flat? Impossible! Okay, so the thrid book was released before any of our times. Actually, come to think of it, he finished the entire trilogy before it was published. So it wasn't like Deathly Hallows, where fans were making theories for two years. (But the Eagles? Faramir/Eowyn? Denethor? Eowyn slaying the Nazgul King? How can you predict any of that!?)

Well, I think the ohhh moment for me was when Harry talked about Draco having become the master of the Elder Wand, and that Harry had "disarmed" (does grabbing them out of someone's hand really count ?) Draco. That was definetly the climactic ohh moment, although I agree it wasn't as well done as in the other books. But JK only had certain solutions, and the fans sure came up with a lot of them.

Minor "ohh"s were Gregorovitch being the wand maker and the diadem being the tiara from HBP. There were more, certainly, but I can't think of them off the top of my head.