Everybody knows the phrase, and knows it comes from Ray Harryhausen's final "Dynamation" film, 1981's Clash of the Titans. YouTube link
And of course the 2010 remake (a bit more forceful): YouTube link
But neither are the first appearance of the phrase, nor the most dramatic.
Instead, that honor goes to…
Thundarr the Barbarian, "The Attack of the Amazon Women" !!!???!!! (1980)
Alas, no clip. But I was watching this episode last night (possibly for the first time— I don't really recall much of the show I saw back then)— and there it was.
The evil Amazon sorceress Stryia shouts the phrase, very triumphantly, and out of an undersea vault swims a giant octopus thing with webbed tentacles that can shoot some sort of laser beams from their tips. It also has eyes and a mouth with fanged teeth on the top of its head, so it "looks forward" as it swims. Alas, no pic of it either.
However, I did find a blog with a picture of Stryia, the character who starts it all:
Did Harryhausen know of this use? Or is it just coincidence?
And is there an earlier use out there?