Steven laments that he can't figure out how to summon his weapon, and he says at least he has Cookie Cat. He takes a bite... Cue his gem glowing like crazy, the Gems' shocked responses, and the theme song blasting in the background to reveal...
Pearl: Steven... It's a shield!
When Steven fearlessly stands up to the centipeetle mother saying "LEAVE THEM ALONE!" holding ice cream and ready to kick ass.
When he realizes his powers suddenly no longer work, he uses the smashed freezer to electrocute the centipeetle mother, giving the gems an opening to destroy it.
Garnet: Gems! Weapons! (They summon their weapons.) Let's do it.
"Laser Light Cannon"
Steven activating the light cannon and using its power to destroy the red eye. And the beam the cannon shot formed a shape that looked like Rose Quartz. That whole damn climax was pretty awesome.
Garnet: BRACE YOURSELVES!
When the Gems can't figure out how to get past a magical whirlpool which has gravity several times higher than normal, Steven ropes together some spare sweaters, loops them to the other side, then climbs the wall by himself. Even Pearl, who is extremely concerned for his safety, admits that was cool.
Amethyst (carrying Pearl and Garnet): Steven-style!
Garnet casually knocking down a pillar with ease to make a makeshift bridge.
Steven shoves his demonically-possessed breakfast into a melting pool after it's mutated into a giant monster and taken out the other Gems.
Steven manages to beat the giant worm by tricking it into wrapping itself around the dock, which then collapses from the strain and crushes the worm. Particularly, he was able to move quite nimbly, showing off Acrofatic at its finest.
Not to mention summoning the titular bubble, to save Connie from a collapsing chunk of cliff.
Garnet dragging away the nosy Amethyst and Pearl. Not to mention her line:
"Don't mess with his funky flow!"
Onion knowing how to operate a harpoon gun despite his very young age, and his hilariously nonchalant/triumphant reaction as his boat is sinking.
Not to mention her off screen moment of awesome as she carried Steven over a room cover in spikes, guillotine and pouring lava.
As soon as Steven figures out what's going on, she turns and starts punching the floor without a word.
The short but oh-so-awesome smackdown between Garnet and Amethyst.
Watching The Purple Puma ruthlessly pwn everybody is not only entertaining to watch it's oddly satisfying as well.
The whole sequence after Steven throws the desert glass on the beach and then he tries to get it back with all these structures shifting around in this big sandstorm and Steven's climbing on stuff and oh no he's going to fall on those spikes. Then the Pink Lion swoops in and The Awesome hits the fan. It starts the awesome train by ROARING AWAY a bunch of Sand Structures that even Garnet couldn't make a dent in, using one of the structures it broke to get up to high ground, leaps like 15 feet through the air and bursts through the structure the Desert Glass made to protect itself using it's roar and looking cool doing it.
Garnet's brief but epic beat-down against the monster at the beginning.
It's mostly off screen, but there's a brief few moments of the Gems moving in complete tandem as they presumably lay waste to the smaller parasites.
Opal versus the giant bird, with the background music combining both Pearl and Amethyst's themes.
When the bird splits apart into hundreds of attacking birds, Opal orders Steven to stay low and then proceeds to fuse Amethyst's whip and Pearl's spear into a bow and arrow, which she launches to destroy all of the birds simultaneously. And all while en pointe, no less.
Pearl's finishing move against Amethyst in their game of checkers.
Pearl and Amethyst display incredibly fast teamwork to save Steven when he almost falls to his doom.
"So Many Birthdays"
Assuming Steven will age in real life like he did when his gem "malfunctioned", looks like he'll grow up to be a tall, muscular, still adorable, and frankly pretty awesome looking guy.
The efforts of the Gems to revert Steven to his proper age are quite admirable when given the extremely bleak circumstances. Special mentions to Amethyst, who never gave up and kept trying to motivate the other gems as well as Pearl, who despite being in the midst an obvious breakdown, realized that Steven's age was fluctuating based on his moods and therefore provided the key to his eventual age reversal.
"Lars and The Cool Kids"
Steven verbally tearing into Lars when he blames the magic moss on Steven's "Weird mom".
Steven saves the day without any help from the Gems whatsoever this time, and manages to snap Lars out of his freakout to get him to help the other kids.