Seconded on this one. Being a kid who LOOOVED dinosaurs, when I saw that scene I gasped, but I think my heart literally stopped for a second. When the dino THUDS down onto the ground and everything shook I felt chills. Absolutely powerful scene.Seeing the Brachiosaurus in Jurassic Park.
One that had a similar effect on me was the first transformation scene in "Transformers" (Blackout attacking the military base). I saw that scene at a preview event months before the film opened, so no footage or commercials had come out yet of actual transformations on screen. The seamless conversion from helicopter to robot was jaw dropping to say the least.