Rose: You want me to break up with Jake? I could never hurt him. I know that sounds weird from someone who spent the last year trying to slay him, but I could never break his heart! Or my own...
Jake sets up a private ball for him and Rose at "Homecoming," and promises that he'll be there for her when she leaves the Huntsclan.
After Rose attempts a Heroic Sacrifice by wishing for the destruction of the Huntsclan, Jake wishes that Rose was never taken by the Huntsman to save her. He had the chance to wish for anything else: that Rose would be spared, that she was his girlfriend... but instead, he gives her the chance of a normal life with her family, even if it means that she won't remember him. Jake has proven how much he loves Rose by letting her go.
Grandpa putting his Halloween candy in Haley's bag when she wasn't looking, so that she'd think that she got more candy than he did.
Jake and Rose's kiss in both "The Academy" and "Hong Kong Longs".
Made even more heartwarming when you remember the early season 1 episode "Act 4 Scene 15", in which they had trouble with the kiss scene in Antony and Cleopatra because, according to Rose, that kiss represented the culmination of what the protagonist had gone through together and Rose and Jake had not going through anything together... Yet.
Jake and his dad Jonathan's talk at the end of "Hong Kong Longs."
Jake: Dad, you just found out today you married into a family of magical reptiles. You seem to be taking it pretty well.
Jonathan: I don't know. I guess, deep down, I always knew there was something magical about my family.
Jake: Trust me , there something magical about you, too.
On the subject of Jonathan, the episode where Jake travels back in time to when his mother and father were still high school sweethearts, to see if Jonathan would be able to handle his family's magical nature. At first he, somewhat understandably, freaks out, but after Jonathan is approached by the Huntsclan and asked to reveal his knowledge of who the dragons are, to help wipe out the "monsters", Jonathan refuses, and states that the only monsters there are the hunters.
This incident also qualifies as a crowning moment of awesome.
Jonathan: Well, as soon as I saw it, I went looking for you kids. Nothing's gonna happen to you on my watch, Jake! Jake: (smirks jokingly) Cougar Scout Code? Jonathan: (sincerely smiles) No... Father Code.
In the Season 2 theme when Jake high-fives with a cute little elf.
There's a subtle one in "Breakout," where Rose just stares at Jake when he stammers his justification in spending time together. Her glance read, "God, this guy is too adorable."
Rose not getting scared away from Jake's admittedly disgusting moulting cycle, when even Trixie and Spud couldn't help but have a near-puking reaction whenever they saw him during that.
Also, Trixie and Spud inventing a cream to get the moulting skin away faster.
In "Furious Jealousy", Jake goes on a junk food binge due to the lack of dragon business lately, which results in him gaining so much weight that he can't defend the town or his friends. By the end of the episode, he agrees to go on a diet, just to protect them.
Leads into Nightmare Fuel: If Fury and her sister's hadn't shown up then and had left to go and plot, how big would Jake have gotten? He'd've had a heart attack or been unable to win, even with the help of his friends.
In "Bite Father, Bite Son," Lao Shi explains to Jake that part of the reason he was chosen to be the American Dragon was because of Jonathan, who Lao Shi describes as "courageous, kind and honest," and a good example for Jake to follow. This becomes even more heartwarming when you consider that Lao Shi utterly hated Jonathan when he and Susan were dating back in high school, showing that his opinion of him has improved greatly since then.
As for Haley, any time she recognizes Jake's worth or how much he's willing to do to protect her or his magical charges is guaranteed to warm your heart.
Nobody mentions the episode where Trixie and Spud learn Jake's a dragon. After learning the secret, instead of just freaking out or the like, they state they're always going to be his friend no matter what.
Even more so beforehand, Jake's grandpa has Fu Dog create a potion to erase Trixie and Spud's memories of the incident due to the Dragon Council. What does Jake do? He gets rid of it. That's how much he trusts them.
In "A Hairy Christmas", Trixie is bummed out for the majority of the episode because her dad is iced in at his Air Force base all the way over in Greenland, and won't be able to make it home to New York City in time for Christmas. Then come Christmas morning, she is surprised and overjoyed to see that her dad made it home! When she asks how, he states that something flew over the base and melted away all the ice, and jokes that he didn't know Santa's reindeer could breathe fire. But Trixie, along with the viewer, knows better: it was Jake. He flew all the way to Greenland and de-iced the base just so his friend could spend Christmas with her father. If that's not a Best Friend, I don't know what is!