Cassius in the semi-finals of Robot Wars season 2 where its self-righting mechanism was demonstrated for the first time receiving a loud cheer from the audience and several replays. Watch it here.
Made all the more awesome by its sheer unexpectedness - hard as it may be to imagine with so many subsequent robots using a self-righting mechanism, at the time nobody except the designers knew that the flipper could or would be used in that way. The designers claimed that they hadn't actually intended the flipper to be used that way and improvised when Cassius found itself immobilised, but only they know how true this is.
Especially since the flipper was not particularly effective as an offensive weapon.
And the fact that, up to that point, Sir Killalot's ability to turn its victims over had been the reason it was the most dangerous house robot.
Cassius's predecessor Recyclopse's crowning moment of awesome occurred when if flipped over Matilda, the first 'House Robot Kill' of the series (also consider that Reclyclopse was unable to move at the time). Cassius would later repeat this feat.
In the sixth wars newcomer Dantomkia received a Crowning Moment of Awesome by flipping Chaos 2 out of the arena!
...and in the seventh wars, Gravity flipped Dantomkia out.
This one requires elaboration, at that alone won't do it justice. Gravity flipped Dantomkia out in roughly SIX SECONDS, setting the record for the shortest battle ever. And the kicker? The previous holder of the Quickest Battle record was also Dantomkia, in its previous fight no less, who took out IG-88 in 8 seconds. Glorious.
And when Chaos 2 won the 4th Wars, becoming the ONLY robot ever to maintain the championship (or even win it more than once).
The Series 7 incarnation of X-Terminator and the American Cyclone Raptor, whose flywheels were so powerful that they could spin opponents right out of the arena. Both managed to do so twice.
While it may not be as universally liked, the fight between Bigger Brother and Hypnodisc shows the former getting ripped apart and still win. Even the announcer was going through its death speech before they managed it.
Razer whenever he is attacking the house robots, which is nearly every fight as seen here
Every one of Razer's appearances in season 5. In each of the preceeding three seasons, debilitating mechanical faults meant Razer was knocked out by the third round, and everyone, even its fans, were expecting a repeat. Cue unmitigated destruction of every single one of its opponents, culminating in a dominating fight against Bigger Brother in the finale and Razer being awarded the well deserved title of the winner of Robot Wars.
Well it was the first to outright destroy a house robot - watch this
Any instance of the competitors abandoning the battle to go after the House Robots will often make for a CMOA; probably the best example would be the first melee of the Seventh Wars All-Stars Tournament, where Kat III, Panic Attack, Bigger Brother and Firestorm all made a pre-match pact to go after the house robots - Shunt, the Refbot and Cassius Chrome - instead of each other. It's hilarious to watch, especially as the arena tries to fight back and fails, setting off the floor flipper and drop zone in a desperate attempt to catch out the competitors as they give the House Robots a thorough pasting.
Panic Attack received several during it's season 2 (its first appearance).
1 - during it's gauntlet run it was going over the see-saw ramp, but Dead Metal was underneath it and Sir Killalot was coming up from behind, both preventing the ramp from going down. What does PA do? Tries to jump off the ramp and over Dead Metal (it didn't work, but still...)
2 - Knocking Shunt of the sumo-ring in the trials.
3 - Knocking out Sgt Bash's saw while fighting Whirling Dervish.
4 - Defeating Mortis during the series semi-finals by pushing it into the pit.
5 - Defeating series favourite Cassius in the grand final by pushing in into the pit as well (and earlier in the fight driving right over the top of Cassius) and becoming the grand champion of the second wars.
The Plunderbird team during season 2, when playing their theme song!
Firestorm, in the Commonwealth carnage, somehow managed to flip Mr. Psycho! Keep in mind that Firestorm weighs 99kg, while Psycho weighs 750.
GBH: since the last season, it had received an "upgrade" which seemed to consist entirely of a more ornate casing. Before entering an Endurance Tug-o-War against the house robot Matilda which seemed to be a Curb-Stomp Battle, the team makes oblique references to a "secret weapon". As expected, Matilda quickly overpowers them, but as she pulls on the rope the robot leans forward, causing its ornamental spikes to embed themselves in the ground, slowing it long enough for it to exceed the previous record. See it here.
Warhog's design attempted to one-up Hypnodisc - its entire body was a kinetic energy weapon, covered in blades and spinning at high speed. Theoretically, such a design should provide amazing attack and defense. Unfortunately, they neglected to reinforce it - each time it rammed an enemy it was sent flying into the air while its opponent took minimal damage. After a few rams it had ceased functioning in a most awesome fashion.
The Typhoon series of robots later did this to greater success, holding several victories in the middleweight division and Typhoon 2 winning the grand final of the seventh wars (via one of the most controversial judge's decisions in the series. Literally noone was happy with it, including the judges themselves)
Except Jayne Middlemiss, who was rooting for Typhoon 2 all the way because she was Scottish and Typhoon 2 was a Scottish robot. Go figure.
Wild Thing's heroic performance against the horrific destructive power of Hypno-Disc in the 4th wars semi-final, not only being the first robot to actually survive a battle against Hypno-Disc in that series without being totally dismembered, but nearly winning the judge's decision through the courage and tenacity of their fightback.
Another CMOA relating to knocking a robot out of the arena, Storm 2 did this to the Steel Avenger. Only Storm 2 didn't do it with a flipper; it did it by pushing Steel Avenger into a wall at high speed, where it just bounced over the fence. Now that was cool.
From Robot Wars Extreme Warriors (the US version), we've got Tricerabot the House Robot killer. It flipped a flywheel-bearing Matilda, and shoved Sir Killalot into the pit (which wasn't shown on TV). Keep in mind, this was the season BEFORE it even had a flipper.
From Series 3 Grand Final we have (again!) Chaos 2. After defeating Hypnodisk it tried to keep the Housebots away from his defeated opponent, and when Matilda and Shunt ganged up against it they got flipped over with ease. And probably Chaos 2 would have got more if cease wasn't called. That little black flipper was mean.
Diotoir, the robot that Jonathan Pearce et al were always keen to deride as a joke entry (even inaccurately - he once stated "they've never done well in the Wars", patently untrue when you consider their track record) knocking out Tornado in the Fifth Wars.
This fight between S.M.I.D.S.Y., Warhog, Comengetorix and St. Agro in Series 6. Between Warhog demolishing the arena wall and piggybacking on S.M.I.D.S.Y. twice, and Comengetorix impaling itself on the arena wall by its axe then almost driving down the pit... fantastic.