Nokia 1100. No cameras, MP3s, videos and it has really simple navigation. We have them as standard issue in the office and they are brilliant. Battery life is measured in weeks.
I currently have a Sony and the navigation system is awful - for most operations you need three presses of buttons where one would do.
I recently got a Sony - Ericsson W800i and its great. Its easy to use and has loads of good features like a radio which comes in very handy on my train journeys to work!