Sony Ericsson X10a (AT&T variant). Good and bad memories with that phone. It took FOREVER to get updated from 1.6 to 2.1, never got the update to 2.3 that the unlocked models got, and eventually deteriorated into having random reboots until it finally died. Got a warranty replacement (had to fight to get one), and the replacement eventually suffered the same fate. But it was my first smartphone, was fun to play games on, and took some decent pictures.