SE's current flagship Cyber-Shot phone is the thinnest of this lot, measuring a mere 11mm from front to back.  The C902 features a unique sliding lens cover that actually extends the overall length of the phone when open, and also features a unique touch screen with light-up camera controls.  Only problem is that SE just announced the C905, which bests the C902 with an 8MP camera - or will when it comes out.