A perfect example from Gaiking: Legend of Daiku-Maryu would be in the 13th episode where Face Open is used for the second time, since it was obvious the first was nowhere near epic enough to live up to its namesake. This was.
Though its obvious in this anime you don't need a giant robot to be awesome, as Captain Garis shows when he has to save his daughter Lulu (or Ruru depending on preference of spelling) from Proist. Of course when he has to get past Proist herself who is in Raiking, and him just being a regular man, what does he do? He throws a grenade at it, and whilst Daiya distracts it, battles his way through the army of Robot Lizards - one of which nearly killed him by itself - his own daughter threatens to shoot him out of revenge for her mother, and still ends up saving her.
Anything involving Gaiking the Great can be called awesome. Its only ever used three times, each one is epic. First one here has it kicking the * beep* out of an enemy thats power was so strong, it tore open holes between dimensions. Next has it lifting an entire CITY out of the way of an erupting volcano here. And then to top it all off in its final appearance, Daiya is being overwhelmed by King Darius 18, and is on the verge of defeat. Then we learn he's actually been holding back the entire time to give the others time to free Proist's hostages, as well as shut down all the portals she had opened. As such Daiya can now pull out his trump card, Face Open the Great. The sudden burst of power allows him to catch Proist off guard, and when she catches Gaiking the Great, Daiya ejects the head and combines back into regular Gaiking, before unleashing a Hydro Blazer straight to King Darius 18's face, point blank.
This Troper feels a need to note what was (in his view at least; he never sees any mention of it) Nouza's crowning moment shortly before Gaiking the Great's first appearance; finally breaking free from Proist's control by tearing out the organ Proist had implanted in him, even knowing that it would probably kill him. Yes, you did read that right, he effectively ripped his own heart out. He lives due to Daiku Maryu's intervention, true, but still.
Nouza: What are the facts, earthling scientist!? The fact is that if Daiya can output ten times the flame, then he can beat that shitty bitch? ... Then it's decided. Burn, Daiya. And be sure to waste Proist! Because you're going to be using my corpse as a stepping stone!
Proist: Fool! If you remove that, you will—
Nouza: Go, Daiya Tsuwabuki! RAIKING, PART 1, GO!!!
That's nothing. Right after Gaiking The Great has been formed, Proist has Dborak charge in with a punch, asking Daiya what good he thinks combining the broken giants will do. Daiya then proceeds to do a Punch Catch before delivering this line.
Daiya: Hey. Was that your best punch, Proist? If so, then you lose!