Fantastic Four #2, page 14, panel 5
Uncredited Writer: Stan Lee
Uncredited Penciler: Jack Kirby
Uncredited Inker: George Klein
Uncredited Colours: Stan Goldberg
Uncredited Letterer: John Duffy
This is kind of a cheat, but it is worth pointing out the first time that the words 'flame' and 'on' are used consecutively in The Fantastic Four. Here, the Skrull impersonating Johnny Storm has managed to negate Johnny's flame by flying head-on into him whilst both were flaming. What's nice to see is that despite being in mortal danger, Johnny was actually thinking, 'hmm, those words sound good when said together. I must try them out at some point."
Anyway, even though these are the first time that these classic words are used, the fact that a damn dirty Skrull says them means that they only get a .1 tally. It'll be a little while more before we see Johnny use them as his traditional battle cry.
Check out our coverage of Fantastic Four #2 in our second episode: Secret Invasion Tie-In