As fun as Iron Man 3 was, when the screen goes black and the titles come up, you're smacked in the face with a whole other kind of fun -- the awesome motion-heavy sequence from Creative Director Danny Yount. And, if you thought that was cool, you should see what he originally had planned.
Yount has an expansive interview over at Art of the Title, which you should go read. You can also see videos (which we can't embed here, sadly) of some mockups of his original idea for the treatment, using footage from all three films. Here's where he explains how things turned out differently:
Would you have done anything differently?
I wanted the colour to feel cheap but they wanted it to be film-accurate so we had to pull back on that. I also wanted more campiness and ’70s style tonally but that would have stepped on the film footage too much.
On top of that, additional unused titles were uploaded to imgur a few days ago, showing a totally different treatment from Yount's here. Here's a sample of what those look like: