Mini x10 pro
I have had one of these for the past few months and it's my favourite smart phone so far (had a nexus one as well as an iPhone 3g and 4)
It is the perfect size and is cheap enough not to worry about it scratching/breaking. The physical keyboard is a killer feature in such a small phone and the camera and sound-quality are well above average. It's a little slow sometimes and the battery life isn't great but I work in an office so don't really mind.
One niggle: the headphone/set socket is incompatible with apple style headsets.
Still, I'm pretty sure I'll be upgrading to the new one at the end of the year.