|We're going to need a bigger boat...|
(Click to embiggen)
My favorite of the bunch is and always will be the Silver Centurion. It's funny, I've never read an issue from when Tony was wearing the thing (which will be rectified one day soon), but I just totally dig it. The Silver Centurion just looks so different and cool! I was surprised by the five longest running armors; I was sure Extremis had all of them beat. Glad I was wrong.
Now having said all of that, it's unpopular opinion time: I don't like the movie armors, with the exception of the Mark I. I don't know, they just look too much alike with hardly any real variation. I think the only difference between the main armors in the first two Iron Man movies was the shape of the unibeam/arc reactor piece. The newest armor from the upcoming third movie is mostly in the same boat. It looks like all they did there was swap the red-gold palette, and changed the shoulder guards, the boots, and made minor changes to the helmet and torso.
Hat tip to Geekologie for the picture.