I'll agree I can't see calling an entire city a design icon - parts of it absolutely, but a whole city? Seems too much. Then again, this is an opinion-based idea, so it's not one person's place to deem others' choices inappropriate. And it certainly isn't the place for name-calling.
Five I could come up with, though I did try to avoid repeats (minus that last one):
The 33 Stradale has always been my favourite Alfa, and I don't see that ever changing. Almost named the Vanquish instead - I always felt it was the nicest of the modern Astons, and it really set the tone for proportions for every grand tourer that followed.
A "fashion" watch instead of the more traditional watch makes, but there's something about the ceramic...
I mean this in no disrespect to the lives lost, but the WTC was not a great design icon. The Chrysler building? It's what I think of when I think of giant NYC buildings.
Mmmmm, Eames.
You can love it. You can hate it. But it's all over, especially if you count the influenced and the imitators.
(NINJA-EDIT) Oh, Omnis reminded me. Bonus one: