In Prince Caspian, after a very tiring two-day trek across the wilderness, a lot of stress, and several arguments over whether or not Lucy really saw Aslan, the Pevensies finally meet him at Aslan's How. Peter goes down on one knee before him, takes his paw in both hands, and brings it to his face, and apologizes to Aslan for not having led them all better.
Aslan at the Bridge (formerly the Ford) of the Beruna River:
Before they had begun to cross [the bridge], however, up out of the water came a great wet, bearded head, larger than a man's, crowned with rushes. It looked at Aslan and out of its mouth a deep voice came.
"Hail, Lord," it said. "Loose my chains."
"Who on earth is that?" whispered Susan.
"I think it's the river-god," said Lucy.
"Bacchus," said Aslan. "Deliver him from his chains."
Later in the book, during Peter's duel with Miraz, Caspian frets that Peter will allow the jeering of the Telmarines to goad him into acting foolishly. Edmund calmly declares his faith in his brother: "Not he. You don't know him."
Reepicheep's people revealing just how devoted they are to their leader, and then Aslan paying back not just the mice's loyalty, but the seemingly innocuous kindness of them chewing off his bonds at the Stone Table centuries ago (shortly after which is when Talking Mice first appeared, according to the book) by restoring Reepicheep's "honor."
Aslan healing a woman on her deathbed, who turns out to be Caspian's childhood nurse.
The Horse and his Boy: When Aslan walks along the mountainside into Narnia with Shasta and reveals all the times he's watched over him his entire life, from his Moses in the Bullrushes incident to protecting him from jackals at the Tombs of the Ancient Kings.
In the same book, Hwin (who has spent the entire book being bossed around by Aravis and Bree) proves she has more figurative balls than either of them when she takes one look at Aslan and offers herself up as his meal.
Aslan's resurrection. Readers will likely have a lump in their throats either in the book where Aslan joyfully rumbles "Yes! It is more magic" or in the film where he's silhouetted by the sunrise.
After the Pevensies are hiding in fear of an approaching sleigh (presuming it could be the Witch), Mr. Beaver braves a look and then merrily tells everyone to come out. It turns out the sleigh is Father Christmas' instead, who is finally able to enter Narnia after so long and he has presents for everyone.
As mentioned above, Aslan's resurrection and how Susan and Lucy run up to him to embrace him.
The heroes are about to charge into (a seemingly hopeless) battle.
Peter: For Aslan and for Narnia!
Though it's also a CMOA.
"We just want our brother back."
You think that's good? That's nothing compared to... "Once a king or queen of Narnia, always a king or queen. May your wisdom grace us until the stars rain down from the heavens."
Peter to Edmund, after Lucy heals him.
Peter: When are you gonna learn to do as you're told?
The end of the Lion, the Witch and the Wardrobe.
"You wouldn't believe us if we told you sir."
From Prince Caspian:
Lucy comforting Peter after the failed raid on Miraz's castle.
Edmund's introduction to the film: Peter's in a fight, is horribly outnumbered and losing badly, then Edmund appears and, without question, leaps in to defend his brother. Afterwards when Peter's obvious jerkishness is established, you realize Edmund knew he'd get no thanks for helping but rushed in anyway. It's a complete turnaround from his attitude in the first film and immediately shows his loyalty to his brother.
Peter handing over his sword to Caspian and finally acknowledging him as their successor as King of Narnia.