I came across this phone yesterday and knew I had to own one. Credit Card Sized Mobile Phone - Simvalley PICO RX-80 | Geeky Gadgets YouTube - Simvalley RX-80 Pico
The best part? They're VERY cheap, $25 / €18. That's if you can get hold of one. I picked one up on Ebay.co.uk for £35 incl. delivery (girlfriend wasn't best pleased though).
Great for a backup phone, emergency/car phone, etc, or to use as a personal mobile while carrying your work BB.
How is this better than a BlackBerry or iPhone? Ok, it's possibly not, but this level of coolness deserves some attention.
You can change the battery though, unlike the iPhone.. Battery life is 100 hrs standby and 1 hr talk time, so again, probably better than the iPhone.