"Rite of Spring", specifically the sequence of the newborn Earth still settling. This troper still gets chills as the bubbles of magma explode in time to the music and the seas come rushing in.
Dance of the Hours. it just reeks of atmosphere. One would have to listen to David Ogden Stiers' narration in the "Making of Fantasia" documentary on the original DVD release to get the full effect.
Although it doubles as terrifying, Chernabog raising his arms to the final stings of Night on Bald Mountain.
Followed by him being driven back by the heavenly bells.
The "Night on Bald Mountain"/"Ave Maria" combo. After terrifying audiences with one of the scariest characters Disney's ever devised, the coming dawn brings with it the best possible reassurance that there are still things to hope for. Gorgeous.
Here's something about the making of that segment. The whole "Ave Maria" segment had to be refilmed twice and the final filmreel was flown from Hollywood to the New York premiere just four hours before showtime.
When it was released in 1940, Fantasia was the most expensive film Disney had made, and it was a complete critical and financial flop. Its failure nearly bankrupted Disney, and was one of the biggest reasons (other than World War II) that the studio didn't put out another full-length animated feature until Cinderella. Nowadays, it is often regarded as not only Disney's best feature, but as one of the greatest films of all time, making Fantasia a standout example of Vindicated by History. If that's not awesome, I don't know what is.
Most of the time, Toccata and Fugue in D Minor is performed on an organ, but Fantasia opens with a full symphonic arrangement of the song that is sure to enrapture the audience immediately. What better way to begin Fantasia than this sheer Crowning Music of Awesome? There is also something about the vague, surreal imagery that accompanies Toccata and Fugue (in comparison to, say, the more story-driven imagery of Rite of Spring) that somehow serves to highlight the beauty and intensity of the music greater than any other imagery could have done. The kicker is the very end of the piece which seamlessly synchronizes erupting water jets with Stokowski's conducting motions, and the final image of Stokowski silhouetted on a sunset as the final, haunting passage of Toccata and Fugue plays is guaranteed to hold viewers in awe at the combined evocative power of music and imagery.
The Sprite's revival in "Firebird Suite". She has suffered a horrific Disney Death — being swallowed whole by the Firebird — and has just been revived by the Elk. Ashen, she understandably blames herself for (innocently) waking the Firebird, but he has faith in her ability to restore the decimated forest. (This is all apparent to the viewer without dialogue.) He carries her toward a little tree, the one she had tended to shortly after she was awakened, and she begins to cry - and the tears immediately start to regenerate the forest. Realizing what's happening, she shifts into the form of a wave...in mere minutes, the forest is revived and more beautiful than ever before, to the point that even the bare parts of the volcano that she hadn't been able to vivify the first time around are now lush and green. She finally dissolves into the wind as the Elk looks on. "Awe-inspiring" is too mild a term for it.
The Firebird itself is pretty awesome, too, even while being one of the scariest things Disney ever put on film. Gives chills when the Firebird makes his entrance. Best use of a Scare Chordever.
"Pines of Rome", AKA the flying whales sequence. Especially the last three minutes. Sure it's bizarre and surreal but there's just something about that combination of the whales leaping up from the clouds and the majestic sweeping EPICALLY gorgeous music.
That shot from the underside of the 'armada', if you will, slowly spinning around to look forward, into the sun...
Disney's done some Al Hirschfeld homage before (the Genie in Aladdin, for example; sequence director Eric Goldberg was the Genie's lead animator), but the "Rhapsody in Blue" sequence really brings home everything about Hirschfeld's career: the distinctive design of the characters, the love of music, the love of New York, and the love of the theater. The fact that it's all done with George Gerswhin makes it a banana split of style.
Always for "Rhapsody in Blue", Duke gets one for deciding to chase the dream and earn his happy ending... and being indirectly responsible of the three others obtaining their happy endings!
"The Steadfast Tin Soldier": Said soldier comes back to save his love and throw the Jack-in-the-box in the fireplace.