Delivering the ZEUTH vs ZEUTH scenario, which is built up for the entire first act of Z, while making the scenario completely controllable by the player (resulting in a very high HSQ when the player realizes this is actually going to happenandit's fully playable).
Super Robot Wars Z 2.1 Hakai-Hen
In Scenario 18-A of the third route split in SRW Z2, which takes place during a concert in the Macross Frontier storyline, Sheryl Nome's song "Iteza Gogo Kuji Don't be late" pumps up the heroes so much that they all instantly shoot to 130 morale. After defeating the initial enemies, Baron Ashura arrives with some Kikaijuu; this causes Ranka to take the stage and sing her song "What 'bout my star?", which pumps Simon and Kamina up even further, to the point that Kamina debuts Gurren Lagann's most famous attack, the Giga Drill Break(er), nearly obliterating the Kikaijuu Toros D-7 with it.
Simon and the Getter Team getting their midseason upgrades in Scenario 40. This event also allows Mushashi the chance to pilot Shin-Getter 3, which is in itself a moment of awesome for both Musashi and Banpresto as this has never happened in the 20 years of the franchise.
Elgan Laudic, a supporter of ZEXIS who has lived for over 200 years and was a friend of Aeolia, gets one when he breaks into an office room in New York and shoots both Stinger and Cohen flat out.
Super Robot Wars Z 2.2 Saisei-Hen
In one of the early stages, Setsuna in the broken down Gundam Exia goes up against multiple A-LAWs and Suzaku on his own. After Suzaku critically disables the Exia, things look bleak until ZEXIS shows up, and Setsuna relaunches in the brand new 00 Gundam. Poor Spinzaku has nothing on the Twin Drive...
Lelouch gets one on his own, not as Zero, but as normal student Lelouch. Terrorists have a large portion of the student body held hostage, during the Couple Event along with Lelouch. What does he do? Distracts them long enough for everyone to get away, leaving him alone with a bunch of angry terrorists. Then he gets saved when several members of ZEXIS burst in from the window.
Carlos Axion, Jr. taking it upon himself to seal a ZONE with a new device invented by Traiya, despite not having a Sphere or being a combat pilot.
Elgan Laudic gets another one: spoiler
Since he is the Z2 universe's version of The Edel Bernal, he fears that he may lose control like his Z1 counterpart did upon learning about the Black Knowledge, placed a clause in the Federation's charter when he was the Secretary General of the United Nations. That clause? No matter what the Federation does, ZEXIS will have supreme authority to police the Earth if it is reformed. Not even the A-Laws or OZ can overrule this clause either. And he did this while being manipulated by Ribbons Almark.
Not only does it drive Aim away, but it also sends a wave of Vajra away as well. Everyone is surprised by this turn of events (as they were surrounded by the Vajra and Mobile Dolls) and applauds Basara's talents. To top it all off, Basara manages to move a mountain during this. That mountain being Chirico Cuvie, who actually SMILES in response to the song.
Amuro: Ribbons! We don't have as much in common as you think!
Ribbons: Amuro Ray... THIS is the difference between our powers!
When Schneizel reveals who Zero really is, the Black Knights are considerably concerned with the revelation. spoiler
Granted, they just witnessed Suzaku nuke Tokyo and are furious at Zero
. Of all the people to try and reason with the Black Knights, Chang Wufei is the most vocal, calling out the stupidity of Ohgi and the other Black Knights. He goes on to list all of the things Zero promised and followed up on, and to point out that Zero having the power of Geass is irrelevant given that half of ZEXIS possess supernatural powers of their own. Furthermore, Wufei reminds Ohgi and the others that Zero is the supreme commander of ZEXIS, meaning that if the Black Knights want to betray Lelouch, they have to win over their ZEXIS colleagues (who are doubtful of Schneizel's intentions). He also adds that they're obviously emotional and confused following the nuking and are just looking for a convenient scapegoat, which Schneizel gladly provided with his accusations. He rounds it out by saying that if the Black Knights want to fulfill their dream, Zero is their best bet to achieving their goal. Sadly, he only says this on the normal route path where the Black Knights go ahead and betray Lelouch, but considering that Wufei is normally a Butt Monkey in Super Robot Wars, particularly the frequency with which he joins enemy factions as per Endless Waltz, this is without a doubt the single most powerful thing he's done in the entire franchise — and might even be the most powerful thing the character has ever done. Also doubles as Shown Their Work for Banpresto. because
in Gundam Wing's backstory from the manga Episode Zero, Wufei was more of a scholar than a fighter. It was his wife's death caused him to take up arms against OZ.
Ryouma, Hayato and Benkei get trapped in the Mind Rape dimension made by Shin Dragon and are forced to confront their sins. (Musashi is confirmed to have died off-screen). With Michiru's help, they escape being finished off by Saotome. The Invaders wonder aloud what could be interfering with the space that they created when... both Saotome and Anti-Spiral!Nia suddenly scowl with hatred at the Aquarion.
Apollo(nius): "Ba'al... you really are beasts. You who cannot fathom the love and compassion of Man do not deserve to exist beneath the Sun. Ba'al, the Mechanical Angel Aquarion hereby refutes your existence! Behold! The power of mankind... and the power of life!"
Stage 54, full stop. What happens you might ask? Well, you're facing Nia in her mech and things are looking grim, she's about to drop the Cathedral Lazengann on Earth when suddenly Shin Dragon punches a hole through space and time and not only does it appear near Nia, but it brings along some allies that you thought sacrificed themselves earlier in the game. That's right, kiddies! Rand and Setsuko are back!
The IF route version is even better. Nia's gonna drop the moon, but then Holland (who's been absent all game) shows up. Not much help but hey every little bit counts, except Holland can't even finish his big damn heroes speech before Suzaku's buddies Gino and Anya show up on the other side of the map, deciding they'll stick with their friend after all. Then Ozma Lee and Luca appear in yet another corner of the map, finally catching up the Frontier fleet after their adventures looking for Space Whales. Awesome. Now the whole gangs back toget... wait... is that a Dragon coming through space time? Yep. Shin Dragon arrives with Rand and Setsuko in tow. That's 4 simultaneous Big Damn Heroes at once, which is probably a new record for SRW.
Sandman's awesomeness is lampshaded in-game by giving him overblown versions of the Gravion's attacks for his God Sigma Gravion, complete with In the Name of the Moon speeches for the simplest Rocket Punch ("Spin, drill, to break their evil ambitions!") and a shot of the Meido squad in full Squee mode if you manage to land a Dynamic Kill with the drill punch.
Elgan Laudic, the Secretary-General of the United Nations. In Hakai-Hen, he is revealed to be "Portman", the informant who has been supplying Dragon's Hive and Celestial Being with secret intelligence and information about what is going on in the world. In addition, right after Shin Getter awakens, Elgan essentially ambushes Cohen and Stinger in their office in New York and flat out murders them (of course since they're Invaders in disguise mere bullets weren't enough). He tried the same thing on Gaioh, but fails. Then comes Saisei-Hen, where it is revealed that Elgan inserted a clause in the Earth Federation's charter while being drugged and under Ribbons Almark's control that gives ZEXIS absolute police authority over the Earth Sphere should it be reformed, overriding both the A-Laws and the Organization of the Zodiac's rights to that duty. Then, he manages to return control of VEDA back to Celestial Being from Ribbons as well as disclose the truth about the Black Knowledge (and revealing he is the Z2 version of The Edel Bernal) to ZEXIS after having been fatally shot by Ribbons.
NeoSaint'sLet's Play for Saisei-Hen has a number of "Arranged Battles": movies made by editing the attack animations into coherent battle scenes. They start out with simple beatdowns on the bosses, but as the game progresses, get better and more detailed, Telling the story of each battle in their own way. Then you get to the Shin Mazingerbattle against Dr. Hell, and he's actually hacking the game and re-editing the game map to make attacks that are impossible to do in the game (Like Tetsujin 28 and Dai-Guard throwing Missile Mechanical Beasts back at the bad guys. The finale of said episode is particularly epic, with the Rocket Punch 102 Rapid fists (Dancougar Nova and Sol Gravion get their fists in edgewise), ending with a Big Bang Punch/Giga Drill Breaker cross-up.
The Gundam 00 ending: Every single Gundam unit gets some screen time and it all culminates in a duel of Ribbons vs. Amuro and Setsuna with two endings: Either Ribbons jacks the Nu Gundam, forcing Setsuna and Amuro to take him on in the Exia and the Tallgeese, or Celestial Being keeps him from getting away at all and takes him down in Dancougar Nova.
Zxyu0369 also makes good arranged battles. The best one is the arranged battle of Zero Requiem, with ZEXIS vs Emperor Lelouch vi Britannia. Knowing the characters, the battle greatly delivers on tension and drama, in that both sides are fighting each other for peace through different ideals and methods. Fights include Kallen vs Suzaku, Heero vs Zechs, Setsuna vs Bushido, and ultimately many members of ZEXIS against Lelouch himself.