Finn's love of becoming The Hero and doing good and bringing justice to Ooo borders on Yandere. In a good way.
When Finn saves Princess Bubblegum in the original short.
The music behind that scene. There needs to be a full version of that made.
From "The Enchiridion!":
Finn: GIVE ME BACK MY FRIEND! Giant: BUT I KILLED HIM ALREADY! Finn:(Tears) Fine. I'll give your dollar! HERE'S YOUR DOLLAAAAAAR!!! (Groin Attack)
Princess Bubblegum saving Finn and Jake at the end of Dungeon. "Get on my swan!"
The fight scene in Slumber Party Panic. "Smash the pinatas!"
Moreover, even in a world where such weird science applies, creating a serum to successfully raise the dead was a bit of a crowning moment for PB.
Finn faking his death in "What Have You Done?" The Ice King actually bought into this, and let out the pained howls that PB needed to cure the kingdom.
Heck, every other episode PB appears in she gets a moment of awesome.
Marceline's father is going around and, y'know devouring souls. Then he comes across Gunter. Not only does he ask politely for this "Dark Lord"'s soul, Gunter slaps him away. Successfully.
In the same episode, Finn takes down Marceline's Dad by stabbing him in the chest while he was distracted with a Heartwarming Moment, the sends him back to where he came from with the same ritual that summoned him.
While doing an awesome Xena Yell. Why is Finn hardly mentioned on this page?
Finn is made of awesome.
Jake trying to lure the horse with classical music in "The Eyes". It didn't work, but he said something along the lines of "Beethoven's not working on you? Well, HOW ABOUT SOME MOZART?!" complete with Jake starting to play the viola furiously, and it was awesome.
Jake defeating a group of evil gnomes with pure raving energy.
"No more games... No... more.... PAJAMAS!!!"
When Finn FINALLY revealed his hair. That was pretty awesome. And it's blond!
This is worth even more mention by the fact he beat the Lich King. Word of God says the Lich King is an evil so terrible and so powerful that Ice King and even Marceline will run for the hills before him and the trailer setting up his arrival is building him up to be the Ultimate Evil. Billy beat him. Into a tree.
Also, despite the paraphrasing, it means that literally, he didn't use a sealing ritual, or weaken him, he punched him so hard and so much he was sealed in amber from the sheer pummeling.
In "To Cut a Woman's Hair", Finn tries to get Princess Bubblegum's hair. How does he do this? TAKING HER TO THE MIDDLE OF THE WOODS, CUTTING DOWN TREES FOR TABLES/CHAIRS SO THEY CAN HAVE A SPAGHETTI DINNER. That's right. Finn just made Princess Bubblegum an Italian dinner in the woods by just cutting down trees and using a fireplace. Did I forget to mention he's thirteen?
Well, he was twelve during that episode, which makes it even awesomer.
Jake: Finn! Don't do anything stupid! Finn: I can't help it, man! I'm all about stupid! *Jumps into the black hole with a Battle Cry*
In "Mystery Train", when it's revealed that the conductor did it, Finn chases him across several train cars by leaping across after they had been detached from the train.
Jake's gambit through the entire episode deserves mention, as well.
Finn gets on in "The Limit". Jake's on the verge of death from overstretching himself and wasted his wish to get the ancient psychic tandem war elephant they'd gone through the entire maze for. Finn's left with the option of letting Jake die or give up on getting what he wants. What does he do? Wish up the war elephant and have it wish for everyone to be healed and restored. Counts because he actually did something pretty clever.
Not to mention his sheer confidence.
Elephant: Finn the human! Are you worthy to command me? Finn: You know I am. 'Cause you're PSYCHIC!
The two part episodes, "Mortal Folly" and "Mortal Recoil" are gearing up to be this.
Finn and the Ice king teaming up to defeat Eldritch Abomination Bubblegum definitely deserve some credit in the episode too.
Finn refusing to slay the unaligned ant. "Never... never... NEVEEEEER!!!"
Finn jumping off a cliff into a building.
Jake beating up Mr. Cupcake for flexing at his woman.
"Get ready for an upper-cut, you DOG!!!"
Finn faking out the Fight King in "Morituri Te Salutamus"
Even Lemongrab gets a quick one in Too Young. After basically spending a whole episode getting mocked and kicked around, he ends up falling head-first out of the window of a tall tower, and slams his whole head into the ground so hard he has to pry himself out of the hole. And he wasn't even hurt at all! DAMN, that guy has some thick skin!
You know how candy people explode when they get scared? Apparently, according to Patrick Seery (a production assistant on the show,) it's physically impossible for LG to do so. That's how strong his skin is. It's literally impossible for him to explode.
In "Memory Of A Memory" Finn doing something smart and using his memories to show Marceline the memory that her Jerkassex-boyfriend Ash tricked him and Jake into stealing. This is directly followed by Finn, Marceline, and Jake beating Ash down for what he did to Marceline.
Finn faces things that would make grown men run and he does it while he's 13.
"Another Way" is pretty much filled to the brim with this. One moment that comes to mind is when Finn goes frickin' MOSES and plows his way through an acidic river full of ELECTRIC EELS. AND he does it all on a broken foot, AND... Yeah. Still 13.
Again, "Dad's Dungeon" has much of this, but one moment that stood out was when Finn slayed the Eldritch Abomination while Jake beatboxed to a remix of Joshua's pre-recorded messages. It. Was. Glorious.
Wherever you stand on Finn's romantic situation, you have to admit that in "Incendium", Finn's anger in the name of Princess Bubblegum was awesome. He only rises from his Heroic BSODafter his pictures of her were burned, and vowed to kill whoever did it, and then proceeds to freaking shatter a window by kicking it!
PB making a perfect sandwich complete with awesome background music playing along.
Finn changing into demon in "Daddy's Little Monster". As nightmarish as it was, it was also his crowning moment of awesome.
The fact that he could resist the amulet's pure Chaotic Evil long enough to toss Marceline and Jake safely out of the Nightosphere goes quite a way to showing how much of a hero he really is.
In what could possibly also count as a Heartwarming Moment, Finn's final hug-battle against the alpha hug-wolf.
While the way he does so is funny, Finn managing to will himself not to reveal the plan to defeat Goliad to her despite her trying with all her might to read his mind.
