Johnnie Gray deciding to get back his girl and his engine.
Johnnie Gray beating every trap the Union lays for him.
Johnnie Gray finding the General at the Union yard and storming into the cab, retaking his engine at last.
The shot of a locomotive falling through a bridge into a river, the single most expensive shot of the entire silent era.
The engine used in the scene was an actual locomotive that remained in the area for years until it was used as scrap for World War II.
The cannon sequence, keeping in mind all that was done when computers, let alone CGI, were decades away so everything that's happening is 100% real and had to be timed accordingly. To get one shot, Keaton had to measure out the cannon's powder charge with tweezers.
Johnnie clearing a crosstie off the tracks by throwing another crosstie at it, tiddlywinks style. In his usual fashion, Keaton seems completely unfazed as the huge piece of wood flies past his face.
To continue from that, any of the stunts Keaton pulled in this film. No miniatures, very few camera tricks, and definitely no CG: That's a real man running around on a real speeding train, just one wrong foot away from filming his own death.
During the final battle, all three of the members of a Confederate cannon-firing crew were shot by a Union sniper fire, and Gray was the Sole Survivor. Then he accidently threw his sword in the air (which he used very clumsily earlier), and the sword landed on the Union sniper which stabbed him.
Adding to that, when Johnnie was trying to fire the cannon, he accidently made the cannon muzzle point into the air and the cannonball is shoot nearly straight upwards. But did the cannonball land straight onto Johnnie and kill him on the spot? No. It crashes behind a wooden dam, releasing a large burst of water the flooded, and washed out a number of remaining Union forces. Even when he's not trying to be a hero, he still manages to save the day.
Johnnie Gray getting an officer uniform and becoming an official solider. Complete with him winning Annabelle's adoration after being scolded at the beginning of the film.
Towards the ending, when a parade of soldiers passed by from the tented encampment, he had to salute them and interrupt his hugging and kissing of his new girlfriend. As usual, he found a solution for that, he repositioned himself so he could do both at once. Romantically kissing Annabelle Lee and mechanistically and automatically saluting the passing soldiers with his right hand.
