Sprint Treo 600. My only smartphone, and I've never activated it, nor would I care to.
I'd probably use my HP iPAQ hx4700 for that sort of thing instead, provided that the media players needed for the Internet radio streams don't somehow fill the meager 64 MB of RAM. (TCPMP works for SHOUTcast and a few other things, but I don't know about Pandora, XM, or Sirius, the latter two of which I thought were satellite radio.)
Even then, I think I'm about to sell the hx4700 and put the funds to an HTC Touch Pro2/ Rhodium W (CDMA variant; still has a GSM modem, also has a built-in 3.5mm jack for headphones, no adapter needed) since they're so cheap now. As much as I like the hx4700, 64 MB of RAM and especially the filesys.exe compaction slowdowns that happen with the NOR Flash used (instead of NAND for devices built specifically for WM5 and later) just aren't cutting it nowadays.