One quick gag early in Aladdin establishes that Iago can imitate voices. Later in the movie he lures Aladdin away from the lamp by pretending to be Jasmine.
In The Book of Life, Manolo's bullfighting skills came in VERY handy when fighting El Chakal. His guitar playing also was useful in order to defeat El Toro in the Land of the Remembered.
In Brave, Merida uses some of her hated lessons (public speaking and history) to calm the three lords when they were seconds away from declaring war on each other. She also uses her not-so-hated skills of archery to help Bear!Elinor survive in the forest.
In Cars, Lightning McQueen learns about backwards driving and opposite-lock drifting in Radiator Springs. Both skills prove crucial at the final Piston Cup race.
In Fun and Fancy Free, Bongo, being a circus bear, puts his circus acrobatics to the test to help defeat Lumpjaw.
During their vacation in A Goofy Movie, Goofy teaches his son Max how to perform "The Perfect Cast," an elaborate fishing technique to ensure a perfect catch. This winds up saving Goofy's life later when Max uses it to catch his dad from falling down a waterfall. Comes up again when Goofy ends up on-stage of the titular concert. Max tells dad to perform it, resulting in Goofy using "The Perfect Cast" as a rather cool-looking dance.
In Home, Oh reflects light off a mirror to distract Tip early on. This comes in handy later when Tip uses it to distract the Gorg driving the Mothership, using the mirror that was supposed to be her mom's Christmas present.
Violet Parr is only able to do tiny force fields, even failing to save her family members from an exploding plane, before finally getting the hang of it midway through and saving everyone every time she uses it.
Dash already knew how to run, but he didn't know what superspeed could really do. He learns a great deal about his power during a chase sequence on the island, running from Syndrome's mooks, such as his ability to run on water. This is called back during the fight against the Omnidroid mk. 10.
Helen's parachute ability.
About halfway through The Iron Giant, the title robot is blown up in an accident, but immediately starts putting himself back together. At the end of the film, the Giant explodes again and is supposedly killed after being blown up by an incoming missile, and moments later, he immediately starts putting himself back together again meaning that he actually survived.
In Kung Fu Panda, Po uses all the skills he learned in his training, like the chopstick fight, in his final battle with Tai Lung.
In the sequel, Po has some difficulty mastering Shifu's "inner peace" form. When he finally attains inner peace and gets the move right, he is able to use it to defeat Shen's battery of cannons.
In The Lion King early on Simba wrestles with Nala as a cub and he never beats her (he finally does as an adult), later he uses these skills to defeat Scar in the end.
The fact that Nala always pins him is one of these in and of itself; it's how they wind up identifying each other as adults.
In the beginning of the film, little Mike sees a Scarer building up the fear in a child by scratching his claws over the child's bedpost. In the final round of the Scare Games and when they are scaring the adults to power the door, Mike and Sulley use the same technique to heighten their fear.
During the library round, the Oozma Kappa use misdirection to distract the librarian from getting Sulley. Don Carlton use this skill again to distract Dean Hardscrabble and the security guards so that Sulley could enter the door to the human world to get Mike.
Learning how to dress and act like a proper lady pays off when Mulan needs to pretend to be a concubine.
The wrap-the-ropes-around-the-pole-to-climb-it trick that Mulan figured out during the "I'll Make a Man Out of You" musical number, which she and her comrades used to infiltrate the Emperor's palace.
The skill of aiming and shooting rockets that the soldiers learn in the Training Montage comes particularly handy, as Mulan first uses it to defeat Shan Yu's army, then to kill Shan Yu himself.
Ling uses the brick-breaking headbutt he learned in training to take out one of the Huns.
Shoe throwing, of all things. Mulan uses it to catch Shan Yu's attention, stopping him just short of chopping Shang's head off. When we saw her do the same to Khan earlier, who knew it'd come in handy?
There's also Mushu's firebreathing. Attempted when trying to impress the ancestors, later used to light the avalanche-triggering cannon, roast the feathers off Shan-Yu's pet falcon, and light the fireworks rocket that sends Shan-Yu to his death.
In Quest for Camelot Kayley defeats Big Bad Ruber by dodging out of the way of his strike at the last moment, causing him to put Excalibur back in the stone, a technique she learned from Garrett earlier in the movie.
A three-second segment of a montage in Ratatouille shows that Linguini's a good rollerskater. This skill proves vital in the climax.
In The Simpsons Movie, Homer manages to earn the runaway Simpson family some money by winning a motorcycle game inside a dome. In the climax, he puts those skills to even better use when he and Bart drive a motorcycle up the dome the town of Springfield was quarantined under, allowing them to throw the nuke out before it blows up.
In The Swan Princess, early on while doing survival training Derek's friend Bromley is instructed to shoot an arrow at Derek's heart and in turn shoot the apple off his head he succeeds, later he uses this skill to kill Rothbart.
In Tarzan, the titular character at one point intimates the sound of Clayton's gun. This leads to a Moment of Awesome in the climax.
In The Tigger Movie, Roo uses the Whoopty-Dooper-Loopty-Looper-Alley-Ooper bounce that Tigger invented earlier in the movie in order to save Tigger from an avalanche (that Tigger himself caused, ironically enough).
About halfway through the first Toy Story film, Woody and Buzz Lightyear actually both get into an argument and fly out of the car they were in. During the said argument, Buzz actually slaps Woody in the face, causing it to spin 360 degrees. Woody then spins his head 360 degrees later in the film in order to scare Sid and save Buzz Lightyear.
Jim Hawkin's solar surfing which got him into trouble at the beginning of ''Treasure Planet' proves to be vital and amazing in the climax when the Planet is self-destructing. He then uses a makeshift surfer using a sheet of metal and a severed cannon to fly back to a portal and change the destination to Montressor Spaceport. His resourcefulness, quick thinking, and Chekhov's Skill save the RLS Legacy and those on board from a very unpleasant demise. Small wonder why Jim is jailbait and Mr. Fanservice at the same time.