Samsung's gone and upped their Ultra Edition 10.9 (10.9mm thick) with the Ultra Edition 5.9, which is 5.9mm thick. For those of you who can't do the math, that's 0.23 inches thick! And instead of trading functionality for thinness like the RAZR, this thing's not actually a piece of shit.
The Ultra 5.9 has a 3.2-megapixel camera, 80MB of internal storage, tri-band, Bluetooth, and a media-player. It may not be a fancy smartphone that runs Windows Mobile, but it is 5.9mm thick, which counts for quite a bit.