Sony Ericsson W200i. It came out in 2007, I believe, and I've had mine since 2008. Basically, it's lasted this long despite the fact I drop it contnuously by accident (a modern marvel in this day and age - it's bloody resilient), and it has pretty much every number I have saved on there. I don't want to upgrade to a smartphone, because I already have an iPod Touch (latest gen.) that does everything a smartphone does anyway save for the Wifi instead of 3G (which often annoys me) and the fact that it's also a mobile phone. I will upgrade eventually, but only when my current phone dies, and it doesn't seem like that will be happening anytime soon. I'm a rare breed in the modern era in that I actually look after things and value things that are built to last...