The Zandatsu move. Having Raiden, Sam or Blade Wolf slice an enemy in half (or more) and rip out their fuel cell before crushing it in their hand (or in Blade Wolf's case, his manipulator tail) never gets old.
The Ninja Run technique. Automatically deflecting bullets with a sword or pulling off inhumanly acrobatic feats by holding down a single button really communicates the incomprehensible speed and power of a cyborg.
The entire Metal Gear RAY Boss fight. It involves Raiden blocking RAY's BFS, throwing the RAY into the air, jumping onto it, running up said BFS, cutting it to pieces, and finally chopping RAY's entire arm off.
The ending of this fight deserves a mention as well. RAY, still not finished, grabs Raiden in its "mouth" and hurls him into the side of a nearby clock-tower - so what does Raiden do? Simple: He takes off like a bullet, running down the collapsing building as missiles and plasma beams rain all over the place, culminating in stabbing the Metal Gear in the head, then sliding all the way back to the ground and stylishly sheathing his blade just as the UG splits in two and explodes behind him. Ladies and gentlemen, welcome to the first five minutes of the game.
The cutscene leading into the fight with Blade Wolf seems tailor-made to pack in as many awesome moments as the developers could think of. It only gets better when the spaghetti Western showdown music shifts flawlessly to heavy metal and the player is thrown into the thick of it against the toughest and most agile foe they've fought yet.
Against Mistral, Raiden demolishes half an oil refinery before backing her up against a tank of liquid nitrogen. He then slices the container open, freezes her, and slashes her to dozens of pieces before shattering her completely.
For the fight's duration, Mistral possesses a dozen extra robot arms and wields a weapon, made of still more robot arms, that functions as either a double-ended spear or a whip at the flip of a coin. Raiden, not to be outdone, can press his assault so viciously that he is able to chop both the polearm and Mistral's extra arms into bits, causing Mistral to retreat in order to rebuild her faculties right then and there.
After being driven nearly insane by the thoughts, fears and regrets of the cyborgs he's fighting, Raiden reverts to his repressed Jack the Ripper persona, and butchers every last enemy in his sight. This alone is enough to give pause to Monsoon, an unrepentant murderer.
As part of this, Raiden has his pain inhibitors disabled, allowing him to feel a stab wound in the chest. Raiden leaves his pain inhibitors off for the rest of the game, and giving in to his Combat Sadomasochist nature makes him a deadlier fighter.
During the boss fight itself, Monsoon throws a whole armored and helicopter division directly at Raiden, who cuts them all out of the sky without moving an inch. Not good enough? He also creates two huge, spinning orbs of debris that Raiden can parry and chop to bits in Blade Mode. By the time Monsoon attempts to use a Washington Monument-esque structure as a combination drill/missile, Raiden simply uses it as a platform to launch himself at Monsoon to finish him in the most brutal way possible.
Depending on how aggressive you are during the fight, Monsoon will either resign himself to his fate, or shout for Raiden to stop. Raiden is so terrifying that he can make a dead-set nihilist who previously didn't care for his own life beg to be spared.
Not only that, but before being kick-planted into the World Marshal logo, Monsoon shouted, "You're dead!", in which Raiden replied, "Dead on!", a phrase he usually used whenever he ripped the mooks' spines. In short, Raiden really knows how to reply to a death threat. Best part? It was just an ad-lib.
When his magnetic powers are active, Monsoon avoids taking damage from Raiden altogether by manually shifting his body parts out of the way of Raiden's individual sword slashes - a feat he can perform with such skill that he is able to continue attacking without interruption, as though his body were incorporeal. Not to mention when he attacks by propelling a stream of body parts at Raiden like machine gun fire, or by separating his legs from his torso so that both halves of his body can attack Raiden in tandem.
After being thrown off a building by Sundowner, Raiden hijacks a Strider UAV and flies it straight up the interior of World Marshall HQ, blasting it to rubble with missiles before throwing said Strider at Sundowner and issuing a recall on all his internal organs.
After a prolonged samurai duel with Sam, Raiden defeats his rival with a single thrust. This reveals that aside from his enhanced draw arm and gunblade, Sam had almost no cybernetic enhancements whatsoever.
How do you defeat Metal Gear Excelsus? By ripping off off one of its three-story-tall Blade Arms and using it to perform Zandatsu on the main body - and that's after you throw Excelsus bodily through the air a few times and use the detached Blade Arm to engage the machine in an obscenely oversized sword fight.
How hardcore is Raiden? Well, when he finally defeated Senator Armstrong, he did it by ripping out and crushing the Senator's still beating heart in his hand.
These two little gems from Raiden during the final boss battle:
Raiden: What's the meaning of life? Why are we here? LQ-84i: [attacks] I am here to kill you.
Later in the game, Raiden and Blade Wolf come across other robot dogs that look similar to him. Blade Wolf mocks them as inferior models to himself by saying this:
Blade Wolf: The stock LQ-84 Fenrir. Unable to speak. A real dog (referring to either himself or the living variety) has far greater intellect.
How about George's response to being held at gunpoint? As a scientist forces Raiden into a Sadistic Choice, George or the surviving kids now being poisoned with chloroform, He grabs at his assailant's gun to buy some precious seconds, and demands that Raiden kill the scientist holding it, even if it means going through him to do it.
Raiden also deserves props for managing to get George's body put into cold storage quickly enough to save his life, too.
Raiden's sword is a tool of justice... but this isn't Raiden's sword.
Crossing over with funny, an honorable mention goes to the souvenir shop owner that not only decided to do business with a heavily-armored cyborg with barely any human features in the middle of Mexico with a robot dog and an auto-piloted car, but also had the balls to spring a tourist trap on him and get away with it.
Ultimately where Raiden ends up at the end of the game speaks highly of how far his character has come. Where before he was manipulated by powerful organizations and people above him, Raiden is now powerful enough to fight back and stop these conspiracies in their place. Raiden is able to single handily fight a one man war against an entire PMC, and all of its resources could do nothing to stop him. Raiden becomes top dog in full control of his destiny because no force on Earth was capable of stopping him, in severe contrast to the puppet that the Patriots made him out to be back in Metal Gear Solid 2.
Made even more awesome by the timing. MGS2 was released in 2001. Rising was released in 2013. It's taken a little bit over ten years, but Raiden has come full circle. Our little pretty boy is all grown up.
Metal Gear EXCELSUS is an impossibly huge mech which makes Metal Gear Ray and Rex look tiny in comparison. It's shaped like a giant spider, and it's two forelegs are HF Blades about as long as a football field. Raiden can parry these attacks.
And before that, a Codec conversation with Kevin reveals that he crossed paths with several Central and Southern American mafias, culminating in them sending ten hitmen with assault gear against him; he won without a scratch with only his sword. Raiden comments that it's not that impressive with cyborg augmentations... Then Kevin adds this happened around 2005, way before cyborg technology became mainstream or even perfected (the only "working" cyborg in this year was Gray Fox). Cue a very shocked Raiden.
Sam fighting Armstrong in his DLC episode. It's impressive enough that Raiden, a full state-of-the-art cyborg, can go toe-to-toe with him, but a normal human in a power suit? This is topped off with Sam clashing with him in the post-fight cutscene to figure out the timing of his nanomachine-hardening, culminating in Sam cutting off Armstrong's arm with an explosive quickdraw. Rest assured that Armstrong proceeding to return the favor does nothing to diminish this. It should be noted that the fight itself is much harder than it is in the main game. Take a look.
While fighting Jetstream Sam, Raiden disarms him by slashing his sword out of his hands, already an awesome moment. So does Sam scramble to retrieve his sword? Nope. He just does a 'come-at-me-bro' pose and proceeds to fight the most deadly cyborg in the world bare-handed. While only having a cybernetic arm and a powered suit.
And what does Sam say after you knock the sword out of his hand?
Sam: Show me a good time, Jack!
It's even better if you're doing exceptionally well against him.
Armstrong: So. You think that little sword can save your master? Haha, well, go ahead then. But make no mistake, Fido. When I'm finished with him, you're next!
Blade Wolf: I was not designed to fear termination. However, directive zero-one is to ensure that all data acquired is preserved and passed along. To expire here... would violate that directive.
Here, Blade Wolf is saying that the act of helping Raiden (and therefore opening himself up to attack by Armstrong) would run counter to his directive of data preservation, which gives Armstrong the fleeting impression that Blade Wolf intends to stay out of the fight. Blade Wolf then continues by saying that he has created his own directives and that he chooses to help Raiden of his own accord. Armstrong gets understandably pissed.
Blade Wolf gets another one in his DLC. He cuts a swathe through Desperado's troops in a bid for freedom, and takes down Khamsin, one of the most heavily-armed Winds of Destruction, in the process.
Khamsin: All this... and beaten by a goddamn mutt.
Blade Wolf: It is said all dogs have their day.
And then Mistral gets one for revealing she planned this from the start just to get him to kill Khamsin, confirm her suspicions about LQ-84i's allegiance, and find a successful means of motivating him on the battlefield.
And before that, the bid for freedom begins with him cutting off one of Mistral's arms in order to steal the range inhibitor controller that she was threatening him with the exact moment he realizes he's gotten an opening. The look on her face is priceless.
Khamsin himself is nothing to sneeze at in terms of coolness. What at first appears to be a mech suit is in fact basically his lower torso, and the chainsaw-axe he wields is so massive that it has built-in rocket boosters just to give him the strength to wield it. Not to mention the fact that both his boss fight and his song, "The Hot Wind Blowing", are the only boss and song created exclusively for any of the game's DLC.