Flemeth has the single most epic piece of cryptic advice ever when she shows up at the top of Sundermount: "We stand upon the precipice of change. The world fears the inevitable plummet into the abyss. Watch for that moment - and when it comes, do not hesitate to leap. It is only when you fall that you learn whether you can fly." She then transforms into her dragon form and flies off.
Varric's introduction: Hawke is pickpocketed by a thug and when s/he turns to give pursuit, Varric bullseyes the thief's shoulder, pinning him to a wall. He then strolls over, dishes out some snark, collects the money pouch and hands it to Hawke.
Varric: I knew a guy who could pull all the gold out of your pockets just by smiling at you. But you? You don't have the style to work Hightown, let alone the Merchants' Guild! My advice? Find another line of work. *punches the guy unconscious while he's still hanging from the wall, then pulls out the arrow and lets him collapse*
When we first meet Aveline, she's fighting darkspawn alongside her husband, Ser Wesley. He's injured and prone, and to save him, Aveline tackles the darkspawn and punches it into submission before slicing its head off.
During Varric's exaggerated opening, Hawke and Carver/Bethany are being charged by a group of Darkspawn. Hawke can choose to deal with them him/herself, or let his/her younger sibling take care of it. Bethany incinerates them with a single blast of fire and Carver charges forward with his sword, dismembering darkspawn until only the legs are left standing.
In all versions of Varric's opening, Hawke ends by killing an ogre with a close-up of one of the in-game finishers. Warriors and Rogues get a sped-up version of the classic leaping stab. Mages, on the other hand, summon a pair of giant, spectral hands to grab the ogre, tear at it, and make it explode. It can also be repeated at various points by using Crushing Prison on any sufficiently weakened ogre.
At various points during the game, you're given the opportunity to complete quests by having Varric smooth-talk the bad guys into cooperating (such as convincing a group of Tevinter slavers that the boy they picked up was the Viscount's son, or that an apostate Hawke was an Enchanter sent by the circle to track down malificarum). He's brilliant, and his stories are always moments of awesome. One of the developers has noted that if you let Varric open his mouth, he's already won.
After Feynriel is rescued from slavers, he questions Hawke's motivations in helping him as Hawke doesn't know him. A mage Hawke creates a glowing orb from thin air and tells Feynriel "I am you."
Alistair's cameo if you made him the king of Ferelden. He's just passing through during the Qunari uprising on the way to something even more important, stops to make a few of his signature quips while chatting with Hawke, then continues on his way.
Grey Wardens in general seem to have a habit of doing this. Nathaniel Howe shows up in the Deep Roads in Act III, takes out a hurlock with a headshot that would make Varric green with envy, trades a few barbs with his old comrade Anders, then drops some enticing Foreshadowing about the Wardens and their mysterious new ally.
Varric's Imagine Spot at Bartrand's mansion; it's more or less the medieval equivalent of Scarface and just as awesome.
While dealing with slavers, at one point the leader tells his men to take Hawke. The attack response has this: "I'd make a terrible slave. I talk too much. (Whips out knife and puts it to the leader's throat.) And I do that."
Rogue!Hawke gets one when rescuing Feynriel. "Come no closer!" shouts the slaver, but one of Hawke's responses involves saying s/he's close enough, whipping out a throwing knife, getting a 300-style slo-mo and nailing the slaver in the throat, sparing you a fight.
In gameplay, this generally results from some combination of Merrill, Bethany, Mage!Hawke, and Anders firing off some combination of Tempest and Firestorm spells and slaughtering an entire group of enemies before the battle really begins.
Also a combination of charge attacks set up so that Warrior or Rogue Hawke chains his/her way through literally dozens of Mooks, dealing one-hit-kills left and right.
Bethany becomes a magical Lightning Bruiser later in the game, as she gains the Force Mage specialization, allowing her to put twenty baddies into a tight vortex and then raining fire upon them.
Put a two-handed warrior Hawke in a party with Fenris, then watch the body count rise.
Dual-wielding rogue Hawke and Fenris also make a pretty sweet Battle Couple as well (or a role-inverted Adventure Duo if Silly!Hawke). There's a lot of daggers with Messy Kills, and sometimes you'll get one anyway without the perk.
Emeric the templar deserves a nod for doggedly pursuing his investigation of a serial killer operating in Kirkwall. Sure, he was mistaken about Gascard's guilt, but he correctly surmised that Gascard was connected to the murders. Emeric continues his investigation even after the city guards and his fellow templars dismiss his suspicions.
Emeric: Women are dying out there and no one's doing anything.
A bit of a Funny Moment as well, if you have Merrill with you when trying to root out the group of apostates in act one, one of the mages will try to appeal to her to help them, leading to this:
First Enchanter Orsino faces down an entire platoon of Qunari by himself. The result? They burn. Even better, he takes out the first wave in a single hit. The Qunari try to Zerg Rush him, but from their screams, you can tell Orsino wiped the floor with them.
Hawke coldcocking a Qunari soldier with one punch when they declare war. Perhaps more impressively, Hawke can sucker punch a hunger demon in the Deep Roads.
Our first introduction to Knight-Commander Meredith involves her knocking a Saarebas, a giant and powerful qunari mage, to the ground and decapitating him with one swing.
Fenris ' Offscreen Moment of Awesome during his recruitment quest. While you've been fighting the Tevinters hunting him, he's cleaned up the rest.
Cullen gets one if you side with the mages and have been reasonably respectful to him throughout the game. When Meredith orders your execution, he's shocked, having assumed you were merely to be arrested. Seeing how far gone she is, how crazy she's become, he draws his sword, stepping between Meredith and Hawke, telling her she'll have to go through him.
The entirety of the final battle with Meredith, who dishes out red lyrim-powered attacks with her sword and brings statues to life to attack your party.
The number of NPCs who turn up to help Hawke out is a sight to behold. Cullen and Guardsman Donnic were more or less expected, but realizing that Zevran and Nathaniel had taken the field was a delightful surprise.
If you supported the mages, then after the fight, the Templars completely surround you. You're expecting a Bolivian Army Ending, but after about a long thirty seconds of indecision, Cullen and the Templars back off, and every member of your party walks out of the city alive.
The Templar ending has Cullen taking a step back and immediately bowing, followed by every other Templar in the vicinity as the camera zooms out. In the aftermath, Hawke is crowned Viscount of Kirkwall after its citizens, in Varric's words, "all but begged the Champion to rule", netting you the "Crowning Glory" achievement. Rise to Power, indeed.
Cullen: But they haven't resorted to [blood magic], even to save their own lives. Perhaps if we watch them carefully-
Meredith: And if they hope to escape by playing innocent? Would you accept that responsibility, Cullen?
Cullen: Yes. I believe that's what being a templar is all about.
This quote as well:
Cullen: The Right has always been a last resort, when every mage involved was beyond salvation. The situation was far more dire in Ferelden's Circle, and yet many mages were saved. We could still do as much here.
Grand Cleric Elthina gets one in her first scene: When Mother Petrice attempts to frame Hawke for the murder of Saemus, Elthina listens to her, listens to Hawke's counter, and then politely declares that Petrice is a crazy fanatic who'll face justice.
The Qunari get one in the same scene; when Elthina walks away, a Qunari assassin appears and shoots Petrice dead, then declares that the Qunari protect their own. Elthina doesn't even seem perturbed by this.
Anders' plan to kickstart the Mage-Templar war was a lot deeper than many people realized. He wasn't just thinking "I'll blow up a chantry and then the mages will rebel." He was specifically provoking Meredith. By pushing her into carrying out the Rite of Annulment against the Kirkwall circle for the actions of one apostate who was originally from an entirely different circle, Anders forced the other circle mages to face the fact that the Chantry and the Templars have complete control over them, which set off the chain of events that forced them to finally push back. Despite the flashiness of his methods, he pulled off a Batman Gambit so subtle that even some Genre Savvy players missed it.
If you take Gascard Du Puis with you to save your mother during "All That Remains", it's eventually revealed he's not as innocent as he seems when Quentin offers to properly teach him blood magic. Varric's response? As Gascard starts talking about how eager he is to learn from his master, he suddenly gets a crossbow bolt through his throat, courtesy of Bianca.
Varric: What? You were going to do that, right?
Zevran comes back to fight the Crows if you let him go in the Sundermount caves. The first one gets a dagger lodged in his eyesocket with perfect precision in about three seconds. Even Hawke hardly sees him move. Zevran barely even acknowledged the man trying to sneak up on him before leaving his dagger in his eye, even.
As cool as it is to see Fenris crush the hearts of his enemies, his final confrontation with Danarius takes the cake; he reaches into Danarius' head, lifts him off the ground, and crushes his brain!
Sandal standing hip deep in the corpses of about twenty Abominations, two Desire Demons, untold numbers of Rage Demons and Shades whose bodies vanished on death, and down the hallway, a Pride Demon. Best part is that Hawke encounters him after battling dozens of Shades and several Rage demons in the last room, indicating that Sandal was keeping all of those demons from reaching Hawke.
Hawke: We're cornered. The templars know it. You know it. But this is bigger than their hate, their fear. They've come to take your lives, and we are saying no! We didn't want this, but sometimes... sometimes, you just have to stand.
Silly!Hawke gives an awesome one, as well;
Hawke: So this is it. Some of you are worried; maybe I am too, but I'm not staying long enough to find out. What I know is that I hate being cornered and I can fight harder scared than they can angry. We're getting out, and I'm buying when we do!
The line from Meredith before the final battle, courtesy of Jean Gilpin's delivery. "Blessed are those who stand before the corrupt and the wicked, AND DO! NOT! FALTER!"
At the climax of Act 2 as Aveline and Hawke are ambushed. Aveline cutting a spear out of the air with her sword is cool enough, but then Hawke - even as a mage - tops it by punching a qunari in the face.
At the start of Act III, Elthina effortlessly defusing the riot, then essentially telling Orsino and Meredith to go to their rooms as if they were just a pair of bickering children. And they obey.
Mage!Hawke finishing off the High Dragon Bonus Boss in Act III by calling down elemental fury to fry the beast.
Prior to that, Mage!Hawke finishes off the Rock Wraith by raising their hand and blowing it apart with a magical shockwave.
Really, anytime Mage!Hawke takes down a boss is pretty damn awesome. Particularly Corypheus.
The payoff to helping Feynriel: up until the third act, he's been frightened of his own powers, the Templars, Demons, and every situation he ends up in because of them. Then, at the end of "Night Terrors" he plucks up his courage and decides to go to Tevinter to master his powers; one act later, you're given the job of rescuing a young woman from a gang of thugs, but when you actually arrive at their hideout, you find that the kidnappers are dead. The woman mentions being visited and comforted in a dream by Feynriel, and awaking to find her captors murdering each other- courtesy of the powers Feynriel has finally mastered. Even more awesome is the fact that Feynriel wasn't even in Kirkwall when he did this; he was in Tevinter, having sent his mind through the Fade to assist the hostage!
Bring Aveline along on "Offered And Lost" to interrogate the drunken braggart guardsman in the Hanged Man. Needless to say, she's very unhappy with him.
Aveline: Who? Tell me who! Who bought your honor, and turned a proud guard of Kirkwall into a drunken mabari bitch?
The entirety of the fight with Corypheus in the Legacy DLC.
After defeating him in the actual battle, Mage Hawke duels him with spells in a cutscene and defeats him handily. That's right, Hawke proved to be a better mage than one of the original Tevinter Magisters that entered the Black City!
Rogue Hawke first dodges a fireball with a slow-motion backflip, then knocks him down with one powerful swing to the gut. The coup-de-grace is chucking the Hawke Key straight into his face. If your Hawke is an archer instead, s/he shoots Corypheus with two powerful arrows before finishing him off with one more point-blank arrow to the eye!
Varric starts the awesome right at the beginning of the game; he may have been dragged in for interrogation, held at swordpoint and outright threatened by Cassandra, but by the time he's agreed to dispense with the embellishments and is getting ready to tell the real story, he's settling back comfortably in his chair and lacing his fingers together, fully in control of the situation. Because once Varric gets the chance to start talking, he's won.
Tallis' introduction. She goes through a dozen Antivan Crows like they were made of paper.
Seconds before blowing up the Chantry, Anders/Justice repeatedly slams his staff against the ground like a judge's gavel to shut up Orsino and Meredith while he delivers his Shut Up, Kirk! speech.
Anders: I will not let you see all Mages be treated like criminals! *SLAM* While those who would lead us, bow to their Templar jailors!
Orsino: How dare you speak to-
Anders: *SLAM* The Circle has failed us, Orsino! Even you should be able to see that! The time has come, there can be no half measures!
Hawke: Anders, what have you done?
Anders: There can be no turning back!
Isabela's introduction, in which she singlehandedly defeats three thugs in a bar brawl, then calmly goes back to her drink.
At the end of Act 2: defeating the Arishok in single combat in order to stop him from taking Isabela. It's not an easy battle; the Arishok has incredibly high health and powerful attacks. But when you finally do beat him, it really makes you feel like a hero, especially if Isabela is your character's love interest.
Even better is doing it as a mage. Not only have you just beaten one of the leaders of the Qunari in single combat, but you did it as one of the things they fear most, as the class least capable of close combat.
Before that, Isabela swaggering in with the tome of Koslun.
Standing up to Meredith as an apostate. Especially the part where you can tell her that even after having to put down two insane blood mages in a row, you still chose to let an apostate escape rather than put him back in the circle. You can then stand back and let Anders deliver a full broadside of What the Hell, Hero? in which he explains how all the tragedies you just witnessed are Meredith's fault in the first place, and then watch her seethe as a party full of apostates and rebels walks out of her office, knowing she can't do a thing about them.
During the Act I quest Enemies Among Us, you're tasked with questioning Idunna at the Blooming Rose, who happens to be a mage and, of course, dabbles in blood magic, which she uses to force a Psychic-Assisted Suicide on you. A Warrior/Rogue!Hawke needs help from a Mage party member, but a Mage!Hawke can break the control themself, in a most awesome way. It's the sudden shift from strain to control in Hawke's voice and the resulting Oh Crap from the prostitute that does it.
Hawke: I... will not... be toyed with!
A meta one for BioWare in the writing- first off, there are four bisexual romances and they're made abundantly clear, and that Bioware deconstructed a lot of their usual tropes.