Seabiscuit defeating War Admiral. Admit it, you cheered.
That last race. George pulling back to run alongside the seriously flagging Seabiscuit at first just looks like a quietly heartwarming moment, that at least the once-champion isn't going to finish his last race alone and broken. And that's when the camera pans meaningfully from Biscuit to George's horse, and the audience slowly realizes what's about to happen...
"Have a nice ride, Johnny."
The "learning to be a horse again" sequence is awesome in a more quietly triumphant way, as you realize Smith's words don't just apply to Seabiscuit. That was the first real ride that either Red or Biscuit had been on in a long, long time, and you can see the moment when Red suddenly remembers why he used to love horses.
Smith was looking for a jockey for the jaded, vicious Seabiscuit, and looking slowly between a furiously rearing horse and a jockey in a fistfight, and the entire audience grins as they realize both young fighters are shouting the exact same thing.
"COME ON, YOU SONS OF BITCHES! I'LL TAKE ALLA YOU! COME ON! COME ON!"
The description of Smith's first impression of Seabiscuit.
He said the horse seemed to look through him, as if to say "What the hell are you looking at? Who do you think you are?"
He was a small horse, barely fifteen hands. He was hurting, too. There was a limp in his walk, a wheezing when he breathed. Smith didn't care about that. He was looking the horse in the eye.