Musashi killing a dinosaur by swinging it around by the tentacle-drill it just impaled him with. And still having the strength to pilot the Getter almost immediately afterwards, despite bleeding from the gaping hole in his stomach.
The ever-morbid Professor Shikishima frees himself from the dinosaur holding him hostage by telling Ryoma to just shoot them both, because his life dream is to die in a bloody fashion. To show how serious he is, he asks Ryoma to shoot him with the flashiest weapon he has, remember to photograph it, put it in Shikashima's personal photo album and narrates in detail where he wants to be shot, which of his organs he should lose and how his corpse should lie sprawled out. When the dinosaur shits itself and flees, Shikashima just walks away, dejected that he couldn't get his wish.
Musashi's sacrifice at the end of the original series has permanently etched itself into the minds of mecha fans as the prime example of a Heroic Sacrifice. Anyone who can maintain their heroic resolve while literally melting in the cockpit counts as a Grade-CMOADeterminator.
And it was such a noble sacrifice that one of the alternate OVAs actually put it at the very beginning of the series. Only this one took out all of New York, and the entire forces that the Getter Team had been struggling to fight in the first place.
There's also the lesser-known sacrifice of Benkei, in the Shin Getter Robo manga, which was arguably just as awesome since he was on fire.
The final battle of Getter Robo G is 100 freakin' pages of awesome super robot action. Notable for featuring the first instance of Getter Dragon's Badass Arm Fold pose, used as it rises out of the ocean it was shot down into - a scene imitated in manylateranime.
Gou from Getter Robo Go saves his allies (who pilot Humongous Mecha ranging from 11.2 to 20 meters tall), from an enemy mecha that's even larger by using the Beetle, a scouting mecha that can't be any more than twice his height. And he does it by jumping in the air and spinning so fast that the legs become a drill which rips the enemy in half.
Canadian pilots Sam and Bob Hosner get theirs when they demonstrate the defensive power of their mecha - by casually shrugging off a direct hit from a satellite cannon strong enough to burn entire forests to the ground or destroy reinforced underground military bases. Twice.
Debatably this or when they single-handedly take on the Dragon Turtle, stopping its advance with their tiny machine's body long enough for the Allies' ship to arrive.
Schwarz+Shou saving the immobilised Volga by grabbing its (as described) FUCKING HUGE CANNON!! with their mech and yanking the whole gigantic robot around so its cannon is pointing at the enemy.
Ryoma, who after returning partway through Getter Robo Go, spends pretty much the rest of the series crushing dinosaur skulls with his BARE HANDS.
Anyone else impressed that Ryoma broke a katana in half by catching it with his pecs and flexing it to pieces?
Catches it nothing. Someone stabs him in the heart and breaking the sword while it was in him was his response.
Gou stops the nuclear missile aimed at his allies by leaping in its path with Getter Robo and combining with it as soon as it hits his mech. Slap-on-the-Wrist Nuke indeed.
And then everything that follows. Gou combines with the enemy's Mobile Fortress (which doubles as a One-Winged Angel... made from robot dinosaurs), "swims" through thick layers of solid steel and then just emerges out of the wall on the inside to crush Gol's mech. Then, the total hijacking of said creature which gets reformed into an giant version of Shin Getter Robo with the regular Shin Getter controlling it from inside. It all culminates in the absorption of most of the North Pole, a chunk of the ocean and the Dinosaur Empire's main base, before the now Moon-sized mecha takes off into space towards Mars. They reach it in an instant.
Not to mention they ignore the old rule of having to open get and recombine to use different forms. By this point they have so much Getter Energy that they just spawned the top half of Getter-2, giant drill and all, from the chest of Getter-1.
The whole fact that the Getter Emperor was created by combining Shin Getter Robo with freakin' MARS!
Professor Shikishima is awesome by virtue of the completely off-the-wall weapons he invents throughout the series. His crowning achievement is a toss-up between the missile launcher minigun he builds for Getter Robo or the belt-fed revolver with explosive rounds he hands to Takuma.
The Emperor Machines - the three components of the series' most Humongous Mecha, crush enemy planet Dabeen by combining into it from three directions. This not only destroys everything, but also allows them to use the extra mass from the planet to form an even larger mecha.
When your robot generates enough energy to cause a Big Bang just by combining, you know you're epic.
When one of the plant monsters from Getter Robo Hien attacks New York, America responds by transforming the Statue of Liberty into an enormous Wave Motion Gun, that is wielded by another Humongous Mecha, and opens fire.
The "final battle" in Will of Evolution, between the galaxy-sized Getter Emperor and "God"... who the mecha just punches face-first through a galaxy.
While flying a mecha that is also a bomber Sho and Schwartz are besieged by a swarm of monsters that start to eat their way in. Getting too many holes in a plane that high up wasn't going to be pretty. Cue Sho going to even higher altitudes and constantly pushing the machine to its limits all the while the monsters are falling off or getting cooked to a crisp. When the last one finally dies they're pretty much in the atmosphere. Oh and the cherry on top are Sho's words when they arrive at the rendezvous point with "Sorry we're late." as though they had been held up by foul weather.
Getter Robo: Armageddon
Each series has its own, but the RevivalArmageddon tends to have them all over the place. In particular, the Stoner Sunshine scene tends to take the cake.
And right before that scene, the one-on-one (until the bad guys cheat) fight between Shin Getter and Getter G. Specifically, how it ends, with Shin Getter 1 grabbing part of Getter Dragon in mid-transformation:
Ryouma: C'mon, Doc, can't you pull off a change without checking the controls?
Hayato: Must be something you learn when you're part of a real team.
*Ryouma proceeds to crush Saotome's Get Machine to pieces*
Even better in the original version.
Ryouma: Sorry man, we are able to change even with our eyes closed!
Hayato: That's the difference between development team and combat team.
The debut of the Black Getter, where it proceeds to tear apart one of the invaders with its bare hands, after the Shin Getter itself had so much trouble with it, is way up there, as well.
The entire ending of Getter Robo: Armageddon, where The original Getter Team find themselves in a gap in space-time where they will fight eternally alongside countless parallel versions of themselves from every alternate reality, against innumerable monsters and villains from different dimensions in giant robot Valhalla. Oh yeah, it's that epic.
Any fan of the manga take note: the ending is also the only animated appearance of Getter Emperor. GUHGUHGUHYEAH!
Near the end of Getter Robo Armageddon, the Invaders combine with Jupiter and turn it into a new sun that utterly devours the entire solar system from the moon outward... and is destroyed by the combined efforts of the old and new Getter Teams, who create an enormous Getter Tomahawk that smashes all of Jupiter's moons and cuts the planet right down the center. It even blows the arms of the mecha using it right off.
The nature of the Shin Getter Robo/Shin Dragon combo is in itself a CMOA. A giant robot surfing into space on the head of a giant robot dragon attached to the crotch of another giant robot made from thousands of giant robots combined together? Awesome.
Dr. Saotome stopping Shin Getter-2's giant drill with the palm of his hand. Note that he wasn't piloting a giant robot, though he was standing on the head of one. He then swings the Humongous Mecha around by its drill, before hurling it across the battlefield.
Ryoma gets his in Shin Getter Robo vs. Neo Getter Robo when he jumps from the head of a 200ft tall robot to dropkick a dinosaur in the face. He then proceeds to beat up its buddies - a squad of dinosaurs with guns - by himself, using karate.
Ryoma rescues four falling children by speeding towards them on a rope ladder hanging from the bottom of Neo Getter Machine 1, jumping off and grabbing them in mid-air, then falling several hundred feet (the skyscrapers looked very small beneath them) and onto the roof of a car. They all survive.
Texas Mack. Just... Texas Mack. Even though Shin vs. Neo is commonly regarded as the weakest Getter OVA, Eaglelander Jack King and his giant cowboy robot Texas Mack (also piloted by his sister, and Jack's ranch dog) are generally considered a walking CMOA AND Crowning Moment OF Funny, and reason enough to watch the short series.
During the final assault on Goru's flying ring fortress, after Gou, Shou, and Gai help Ryoma, Professor Saotome, Hayato, and Professor Shikishima go inside the base (They enter by flying the Neo Getter One jet through the hole made by Shin Getter 2's drill). Now, Hayato has a gun, Ryoma has his bare hands and karate greatness, and Shikishima has a gun that disintegrates the dinosaurs. Guess who takes out the most dinosaurs.
Ryoma runs across the street and dropkicks his attackers in the face... immediately after they just shot him in the neck with an animal tranquilizer capable of killing ordinary humans. Note that this was immediately after a fight with three mafia assassins, where he was roughed up considerably and even got a knife buried in his shoulder, so he should've already been exhausted.
A knife which he just had to pull out and throws into another guy so hard that it takes his arm off. Don't stab Ryoma. It just gives him a knife to kill you with.
Really, the sheer awesomeness of Ryoma's three-way fight against Yakuza assassins can't be put into words. Have a video, instead
And after the above, Saotome just smacks him with his geta. Ryoma has just killed three assassins, knocked down his two bodyguards, and should, by all that is right and holy, be on the ground by now from blood loss and a tranq to the neck. *smack*
Ryoma shows us that it's not just the Humongous Mecha that have access to Hammerspace in New Getter Robo. First when he challenges the small Oni army on the bridge while carrying two axes and fifteen katanas, while his arsenal during the assault on the Oni capital needs to be seen to be believed.
The Big Bad watches this assault via magical telescope, and all we are treated to seeing after the initial reveal of Ryoma's inventor... are dynamite explosions that gradually get closer to the gate. And stop. And then start up again inside the city.
Ryoma's moment of sheer insanity in the final episode, where he absorbs enough Getter Energy to single-handedly trash three god-like beings (capable of feats no less than bringing themselves back to life) while piloting the machine so erratically that it almost kills the other two pilots.
You think Ryoma is crazy in this one? Well, you're right, but that doesn't make Hayato any less nuts himself. See this?◊ That's Hayato Jin poking somebody's ears off. And then he claws his eyes out.
Hayato, in this episode, is also able to fight Ryoma to standstill before a bunch of oni interrupt them. Read Ryoma's exploits above this, then remember: Hayato fought him to a standstill.
This troper is surprised no one has mentioned that the final enemy of the series was none other then the Getter Emperor. And Ryoma's response? To Open Get and have his Getter Eagle ram the Getter Emperor!
Sure, it was a watered-down version of Ishikawa's original vision in a number of ways, but the 70's anime adaptations of Getter Robo and Getter Robo G could still be awesome in their own way. Here, for example, is Musashi's sacrifice in the anime continuity.