Probably my favorite Golden Age character who never made it out of the Golden Age is the Iron Ace. He just seems to have the perfect combination of interesting concepts and total insanity to hold my attention and amuse me. (The other main candidate would have to be Micro-Face, whose name alone is made of concentrated awesome/stupid, but Micro-Face's stories tended to be a bit more mundane.)
The story of the Iron Ace starts with this panel.
Golden Age exposition: The only thing faster than the speed of light.
Unfortunately for him, the Nazis do show up.
And so he's shot.
But in a plot twist that's so obvious that you'd have to have such a strong resistance to foreshadowing that I suspect it's more likely that you're actually dead and haven't noticed yet, the Iron Ace's armor leaps forth from the case it's in.
And he proceeds to mete out a helping of ghostly justice upon those Nazis.
Of course, here's the really crazy part: That's not a ghost in there, that's some British pilot who the old man rescued and who hid under the armor, and then climbed into it when the Nazis shot the old man.
And the only thing we know to call him is... Captain Britain. No joke. (Although also no relation.)
So how come this ancient suit of armor is bulletproof? Who knows?
Why was the ancient guy called "Iron Ace?" No clue.
How come the old man made (or rather, modified) a plane specifically for the Iron Ace? Aside from the obvious answer that this was an Air Fighters feature, we can't say.
How is Captain Britain able to run around in the armor as effortlessly as if he's in workout sweats? You've got me. (Dude is insanely strong-at one point, he had a ball and chain affixed to him to hold him while still wearing his armor and casually started beating the tar out of people with it.)
He's just an enigma, wrapped in a mystery, wrapped in an inexplicably indestructible suit of plate armor.