Have you decided which OS you plan to use? Right now your choices are pretty limited:
Windows Mobile
Android
iPhone
Sybian
Palm
Blackberry

Sybian & Palm are pretty much dead and BB seems to be loosing ground fast.
The process to get an app in the iPhone store is difficult (although there is another app store that people can use if they've jailbreak their phones.

Another thing to keep in mind is screen resolution - and if the phone is touchscreen or not.
Personally I like the HTC devices and if I was picking test hardware I'd go with one of those - they make both WM and Android devices.

>Hi All,
>
>Any recommnedations for the best mobile phone/device to use for developing mobile applications on?
>
>TIA