Survival of the Fittest/Awesome

Version 1

Jack O'Connor, managing to crash the terrorists' computer systems entirely with his virus, taking out all the cameras and the V1 ending off the air. Unfortunately this happened, how shall we say? Somewhat late...
- He also gets another posthumous crowning moment of awesome when his virus is reintroduced to the terrorists' systems, poleaxing them again, this happening in version 3 - more than two years after Jack's death.
Adam Dodd's fights with Cody Jenson and Jacob Starr could count, particularly since they were among Adam's biggest rivals in the game (in the second and first half respectively).
- Specially Adam's last action against Cody:

Stapled to a tree was Cody Jenson, a sword through his chest, and 'RAPIST' carved into his chest

Version 2

Bryan Calvert dropkicking Felix Travertil off a roof, causing him to smash through the skylight of the adjoining antebuilding. Badass? Why yes, yes he is.

Version 3

Darnell Butler laying out 'Boxer' Carvalho, who was more than seven foot tall, and built like a brick wall, in what amounted to one punch. This coming after Darnell just killed three people who attacked him. Beware the Nice Ones indeed...
- For reference, Darnell is a foot shorter and almost one hundred pounds lighter than Boxer.
Sean O'Cann's very Deadpan Snarker -esque sarcastic comments when cornered inside a room between two of the island's resident murderers: Gabriel Theobaldt and Dominica Sharpiro, are his Crowning Moment of Awesome.

Sean: You see why I call the guy a lunatic? * he frowns, having been called a young virgin metrosexual'* Hey, enough about my sex life: just concede that I have a far higher chance at getting laid than either of you and be done with it. Hell, it would be a minor miracle if Gabriel could meet any woman and spend more than a minute without disembowling her. * He looks at Dominica* And rest assured, I would come up with a suitably witty remark concerning you, however, I have no fucking clue who you are.

Character Derailment notwithstanding, the SADD vs. Blood Boy (one of the bigger villains of the first half of version 3) fight was one of the most action packed and all-around awesome moments of the third game so far. Read it here (the action starts at around page 4).
- In addition to this, the scene also manages to encompass a Crowning Moment of Heartwarming and Tear Jerker.
Speaking of SADD, Bobby Jacks' encounter with the group is definitely one of his best moments. Keeping his cool in the face of a giant Mexican Standoff (Bobby vs. Everyone else) Bobby manages to calm down the situation, and when things finally go to hell, both walk out of the fight completely unscathed and kill three people, granting him the distinction of being the only guy to pick a fight with SADD (the largest group in Survival of the Fittest v1-3) and come out on top. The Thread.
When you finally learn about what happened to the students in V3 that disappeared... Especially Bill's Heroic Sacrifice (along with Darnell Butler, John Sheppard, Jessica Jones and Derrick Taggart). The explosion? That was him destroying the armoury and taking an entire fucking platoon of Danya's soldiers with him. Then comes the final battle on the beach, which ends on a cliffhanger. EPIC.

Version 4

It's still early in the game yet, but the entirety of Ethan Kent's Self-Sacrifice Scheme in The House of the Rising Sun definitely sets a solid precedent.

Ethan: "If I’m going to die, I want to be taken out by the final boss, not by some kid from the chess club. I don’t want any of your circuitous bullshit about a classmate killing me. In the end, it’s you. If you hadn’t done this to us, they wouldn’t be killing. Even if they kill, it’s still you in the end. I don’t want you to be able to hide behind a scared kid. I want my blood on YOUR hands. I deserve to be killed by you."

Eve Walker-Luther also earned one at the hands of Sarah Atwell.

Eve: "Come on! I deserve better than this! Kill me properly!"

The death of Craig Hoyle, who gets shot in the chest, and dies forgiving his killer.

Craig:"Don't blame yourself... th-... people make mistakes. D-Doesn't mean you're any less of a good guy!"

There's also JJ Sturn, who dies ruthlessly beating up his killer, Jimmy Brennan, going so far as to break Jimmy's nose. After being shot in the stomach.
Anna Chase spends most of her game listening to all her friends dying each day (sometimes even watching them die herself). Come Day 9, she finally finds her only friend left, and said friend is almost about to be killed by new killer Kitty Gittschall. Chase decides she's not going to take it anymore, and finally stops her friend's death by hitting her over the head with a shovel and screaming at her to get out. May not sound as impressive as many other feats, but keep in mind that Chase is a 5-foot-tall girl against a known killer with a gun and a baseball bat.
- Also from the same scene, after hearing the commotion mentioned above? In comes Peter Siu. With a gun. And also bitching out Kitty. At this point Kitty acknowledges she's pretty much trapped if she doesn't leave.
Kimberly Nguyen fulfilling her promise of taking revenge on Kris Hartmann and stabbing her to death in retaliation for having wounded her in the arm on their first day on the island.
Somewhat more minor, but Aston Bennett finding Quincy Jones and (with a bit of help from Joe Rios) annihilating him.

"And who better to null my own pain than the only person I truly hate on this island? You disgust me that much."

Her hand strayed purposefully. She fired the gun at Quincy's downed arm, shooting through his elbow.

"Hand slipped." She said, her face cold and unreadable. "The next one won't miss."

Dorian getting tired of all the shit that Mr. Danya has put him through and finally switching sides after shooting him in the chest and presumably killing him just as STAR stormed the island and managed to save around thirty kids from the final hundred... which happened to be a moment of awesome in itself.
No matter how you feel about the mechanics behind it, let's face it; Liz Polanski deactivating her collar using melted aluminum is freaking awesome.