As much as I hate doing it, I have to disagree with Barry. While the walker is without a doubt very cool and super recognizable I have to dispute its "most iconic" status. Without a doubt the most "Iconic" has to be the ANH SD from the opening shot that ship had us "hooked" into the entire story ... 30 years later even. The runner could have had the effect but it flashed past too fast

... the long lingering overhead... that's what made it an icon...

the fact that TESB and ROTJ also opened with an SD shot isn't a coincidence...
Second would have to be the death star. The simple round ball that it is...
I think I could agree it was the most iconic vehicle from TESB, although I think a good case could be made for the Executor.
In case nobody noticed this replay also happens to double as a wish list of "iconic" ships I'd like to see
SD ANH, SD ESB, Death Star, Executor
I do think that SS scale on these would be space prohibitive for me though, I'd gladly put out the cash for these subjects, but I couldn't afford to build the "west wing" onto my house to display them properly
Jedi Dade