Peter hears Susan's horn sounding a call for help and rushes immediately to save her and Lucy, fighting off and killing the Savage Wolf and Captain of the White Witch's Secret Police, Maugrim. It's awesome enough that Aslan subsequently knights him as Sir Peter Wolfsbane, and the deed is twice referenced later on in Prince Caspian.
The rescue of Edmund. The White Witch is almost at the point of cutting his throat when her camp is abruptly stormed by a rescue party of centaurs, unicorns, and Talking Beasts.
Even more awesome in the film adaptation. Edmund is Bound and Gagged, and being watched by Ginabrik. One storm later, Edmund is gone, and Ginabrik is taking his place!
Shortly afterward, after Aslan negotiates with the White Witch for Edmund's life, there's this:
The Witch was just turning away with a look of fierce joy on her face when she stopped and said,
"But how do I know this promise will be kept?"
"Haa-a-arrh!" roared Aslan, half rising from his throne; and his great mouth opened wider and wider and the roar grew louder and louder, and the Witch, after staring for a moment with her lips wide apart, picked up her skirts and fairly ran for her life.
Tumnus deciding to disobey the White Witches order and free Lucy TWICE - even though he knows what happens to people who get on her bad side. Then he runs into a pitched battle with no armor and no weapons. This is better shown in the movie, but it's implied in the book too. He basically follows Edmund's same path only it's not focused on very much in the book.
Everything about Aslan's return, starting with the Stone Table cracking in half and the words, "Yes. It is more magic."
Edmund has an Offscreen Moment of Awesome during the battle. At the beginning of the last chapter of the book, Peter recaps the battle to his sisters and explains how Edmund singlehandedly kept the battle from being lost until reinforcements arrived. Specifically, Edmund fought his way to Jadis and instead of trying to attack her, the mistake every other fighter was making, he attacked her wand, shattering it and destroying her ability to turn people to stone, which gave the Peter's Narnians a fighting chance. This moment was so Badass that the Walden Media film put it on-screen for us to see...and it is glorious!
To add to the above: Peter says that Edmund fought through three ogres to get to the Witch. Y'know, the huge, man-eating monsters of legend? Like Shrek, but murderous and evil? Friggin' THREE of them.
The Professor gets Peter and Susan to at least start considering Lucy's fantastic claims to be factual by pointing out that they themselves admit that Lucy is disinclined to lie or spin tales, that under any other circumstance, they'd believe her over Edmund and that there's no evidence proving her false (this is also in the film).
When the frozen waterfall is coming apart and the children are surrounded by wolves, Peter drives his sword into the ice and manages to keep himself, Susan and Lucy together as the waterfall comes down on them and washes the wolves away.
The big battle scene, or rather, when the two armies clash.
We get a glorious shot of the gryphon flying over the battlefield to report back to Peter, and it shows us the assembled heroic Narnians on the mountainside.
The gryphon reports that the Witch is bringing far superior numbers and weapons, but Oreius shrugs it off, insisting to Peter (also to reassure him) that numbers don't win a battle.
Otmin arrives leading the Witch's forces, and their sheer numbers take up about half of the valley the battlefield is nestled in.
The two armies utter loud war cries as the Witch orders that her army is to give no quarter. Otmin roars and leads the first half of the army out, which itself is a pretty smart move. By only using half of the army, the second half can wait in reserve and save their strength to help put down Aslan's army later after they've tired themselves out - and true to Otmin's earlier planning, this includes their more powerful soldiers like their giants.
Otmin also makes a smart move in not necessarily leading from the front, since he knows that as the general, he's more valuable than the other foot soldiers, and he knows that Aslan's soldiers will be charging spear-first, so why put himself at immediate risk?
Peter actually brings real-world battle tactics into the fight, inspired by the Nazis bombing his home at the beginning of the movie. He has the gryphon flock drop boulders from above the Witch's army to soften them up. Otmin actually stops his advance once he sees them coming, and tries to warn his troops to watch out. Though the gryphons do initially get the drop on the Witch's army, since they couldn't all hear Otmin, the Witch's archers recover and begin picking off the gryphons, ending their attack and forcing them to scatter.
Finally, we get the big moment, as Peter cries, "For Narnia! And for Aslan!" He and Oreius charge, followed by their forces who also rally for Aslan. The scene that follows is nothing short of majesty, as we cut back and forth between the heroes and villains. The centaurs lower their jousts as they take the head of the army, the felines such as cheetahs, leopards, and jaguars race ahead thanks to their superior agility, and they are met in kind by the Witch's werewolves and felines.
As the armies near each other, the score ends, and you hear nothing but a heartbeat until the armies finally clash in a violent volley of screams and death. Otmin, having allowed some of his forces to overtake him as mentioned above, begins specifically targeting the centaurs with their spears as he knocks them over.
When we cut back to the battle, it appears the heroes have managed to hold their own against the first half of the Witch's army... only for the Witch to lead her remaining troops forward to finish the fight. Peter summons a phoenix which turns to flames and halts the Witch's advance. However, the Witch No Sells it and destroys the wall of flames, forcing the heroes to retreat.
Peter's army has lured the Witch's forces back into rocky terrain, upon which they are met with a massive assault from Aslan's archers.
Aslan, having come back from the dead, brings an entire revived army to relieve the brothers' army and re-introduces himself to the White Witch teeth-and-claws first.
For extra punch in the film, it's implied by the POV camera angle that he outright bites her head off (and possibly swallows it whole).
In the middle of the final battle, the White Witch is using her wand to petrify most of the good Narnians. Edmund, a preteen boy with only a few days' worth of sword training, jumps down on her and smashes the wand himself.
Even better, he's outright aiming for it. Edmund realizes the advantage that it gives her. By taking away the wand's power, he's forcing her to rely on martial prowess instead of her magic, which only Aslan himself had the ability to counter. He's notably the only one shown outright trying to destroy the wand.
Edmund going from a whiny, traitorous, back-stabbing, lying kid brother willing to sell out his family to King Edmund the Just and being totally badass was pretty awesome, you gotta admit.
Peter. He's a teenager. He's given a sword and maybe a day or so of training. HE RUNS AT THE WHITE WITCH AND STARTS FIGHTING HER. Recap: this is a witch who is strong enough to break steel like barley sugar and turns people to stone. Some random kid holds her off with a sword he got as a Christmas present.
Lucy too. You fully expect her claims of a freaking forest inside the wardrobe to meet scorn. You also expect the older siblings to take her side regardless. What you don't expect is for her to get her snark on when she's proven right.
The post-mid-credits scene of the movie ends with the (empty) wardrobe opening, with sunlight shining out, and Aslan's roar.
A giant casually swinging away two Minotaurs with a single stroke.
The rhino charging the White Witch. He had to know he was about to die, but his King needed him, and he was damn well going to answer the call. This troper watched the scene most recently while on a treadmill and hit his maximum target heart rate four minutes into a cool-down!
Aslan himself is a CMOA for the CGI artists. Every inch of him moves like a real lion, is covered in fur (which is an animation nightmare), and blends seamlessly with the environment and characters. And a single frame of him could take over 10 hours to render.
In 2005. There are movies coming out today that can't pull something like that off.
When the fox is distracting the wolves so they won't pursue the children and Beavers, Maugrim rushes past the fox and slips on the snow. The animators took extra steps like that to make it seem more like the CGI characters were really there interacting with their environment. When the wolf lets the fox go, there's a little puff of snow when he falls. The film looks all the better because of the work the artists and special effects artists did. The CGI artists also did an admirable job matching the CGI wolves' coats with the real wolves working in the film.
Aslan showing up to the battle in all his majesty, and the witch seeing him and whispering, "Impossible!"
The centaur who serves as Peter's second in command. Fights at his side for most of the battle, charges the White Witch alongside the aforementioned rhino, takes out Jadis' Minotaur General and even trades a few shots with Jadis herself before getting turned to stone. Absolute badass to the very end. We salute you, Centaur!
His name is Oreius! And he's the hero Narnia deserves! And gets restored by Aslan too, of course.
No love for the red fox? He actually helps Aslan's war effort - and that includes lying to Maugrim's face, surrounded by wolves, about the human children's localization, while they are still around but hidden.
When the wolves figure they have been played and bring him to the White Witch, the fox begs his ruler to forgive him. When the witch refuses to, the fox coldly answers he wasn't talking to her - while looking at Edmund next to her.
When the siblings realise that Edmund has gone to join the witch, Peter and Susan start arguing, blaming each other for what's happened. Lucy yells at them to stop and points out calmly that arguing isn't going to help anything. Not only does she keep a level head despite being the very youngest, she avoids siding with either sibling and furthering the argument and both Peter and Susan silently acknowledge that she is right.
The design team gets points for how the appearance of Santa Claus in the original book was handled here. In the earlier animated adaptation, the character was simply merged with Aslan, but here? Santa gets a complete makeover that makes him more resemble an old warrior who wouldn't feel out of place in Narnia while at the same time retaining his basic design aspects.
Father Christmas tells the Beavers and Pevensies that he's been driving a sleigh longer than the Queen.
Jadis does very well in the battle too. In contrast to the book, where she's implied to rely on her magic turning people to stone from afar (the earlier adaptations use this too), here she fights on the front lines with the rest of her army and proving just why she was able to rule Narnia for a hundred years.
She also beat Peter easily after her wand was destroyed. She would have killed him if not for Aslan's timely arrival.
Jadis tries to assert her authority over Aslan when she's brought to his camp. Aslan delivers a massive Shut Up, Hannibal! - "do not cite the Deep Magic to me, witch. I was there when it was written."
It's doubly awesome when you realise that Jadis is a tyrant who has ruled for a hundred years. The people in attendance have probably never heard anyone talk back to her. Aslan not only puts her in her place, but refuses to even call her a queen - reminding her that she's just a witch whose reign of terror is ending very soon.
Jadis also tries to have the last word, snarking "how do I know this promise will be upheld?" and Aslan responds by roaring at her. In the animated version, she runs away in terror and in the 2005 film she's shocked into sitting down in her litter.
In the book we don't know exactly how Maugrim ambushed the girls but here we see that they snuck up on them while they were playing at the river. Susan deserves major props for keeping her head, distracting Maugrim by throwing a towel at him and immediately blowing on the horn. She also gets herself and Lucy to safety up the tree immediately - and they are completely unhurt when Peter arrives.
You can also see that Lucy is higher up in the tree. Susan clearly made sure Lucy was safe first before worrying about herself. And ensuring that if the wolves jump up to try and get them, they might get her but they won't get Lucy.
Susan may also have missed the battle, but when she sees Ginnabrik approaching the unconscious Edmund, out comes the bow and down goes the dwarf in two seconds flat.
After Lucy gives Edmund the healing cordial - in contrast to the book, where Aslan has to remind her that there are *other* wounded people on the field - she takes one look at it, realises what she can do and eagerly rushes off to heal everyone she finds.