1. Smaug busting out of Erebor, covered in liquid gold, and that spiraling flight into the air to shake it off. Glorious! I wait the whole movie for that moment.
2. Every time Thorin taunts Smaug, and every time Smaug gets even more pissed off and either sprays the ceiling with fire or thrashes around in fury. Both make me laugh with delight. "You have grown slow -- and fat -- in your dotage... slug!"
3. Bilbo and the butterflies. Because it is just so beautiful.
Thorin's "What did we miss?" Also very fond of "Is there no end to this accursed forest?"