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The 4/4s for me. First phone I ever saw and though 'wow that is a thing if beauty'.

Before phones had just looked like phones. But as soon as I saw the 4 I loved it. Still think it's a beautiful bit of design.
 
The white iPhone 4S (by looks, and the addition of symmetrical antenna bands) and the iPhone 5c (by feel, and to some degree design as it feels like a tank).
 
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