Sony Ericsson z520a (2006). Flip phone.
Advantages:
*Can take a beating. I don't know how many times I've dropped it, including on hard surfaces, and it's just a bit scratched up. The battery is a bit beat up from collisions with the ground as well, but still works fine.
*Very good battery life. Lasts more than a week in light use and more than eight hours talking. Also recharges quickly - more than 1% per minute.
*Can take pictures and video and sound recordings
*Can text/Internet, except that it costs money so I don't take advantage of that
*Bluetooth/Infrared transfer options for photos and sounds - which means I can upload my photos for free and download ringtones (or whole songs) from my computer for free
*Works almost everywhere in the world
Disadvantages:
*Pictures are 640x480 max, and thus are kind of poor quality
*Only 32 MB memory so I can't store a whole lot on it. One or two mp3's max.
*Bluetooth isn't the fastest transfer method ever
*AT&T bought Cingular. I like Cingular better. Less shady government wiretapping dealings.
Would I get it again? Yes, if it were the time I bought it. But I don't know if I'll get AT&T again - I don't like them as a company much.