iPhone 4.
Owned the 2G iPhone (hand me down) officially from 11/13/08 until the day the iPhone 4 was announced (6/7/10).
This might be my last iPhone for awhile unless Apple really changes things up and makes it compelling enough for me to stay. Having the iPhone iOS for what looks to be FOUR years straight, I do want a bit of a change by 2012. Watching Android very closely. I probably will still have my iPhone 4 around by the time of my next upgrade and just have it demoted as a back-up phone. iPhone 4 just seems like a keeper. The good news is it has solid enough hardware + software + features that it could endure longer than two years and hold its own against the newer phones including the next iPhone. The 2G iPhone was a classic and ahead of its time, but even after three years, I found it unbearable to use compared to the iP4 and latest Android phones. I hope not to get the same feeling with the iPhone 4 after three years. If some people can use a RAZR for five years, the iPhone 4 can endure just the same if shattering the glass doesn't happen first.