Panasonic P503i HYPER
According to the good folks at Japan Cell Phone Rentals, it was the i-mode enabled Panasonic P503i HYPER that they rented to me for my first-ever trip Tokyo in August of 2001. I forgot to take a photo of the actual handset (duh), but here’s a pic from the Japanese version of Wikipedia:
I seem to remember that either this phone or one I rented on a subsequent trip wasn’t actually silver — it was “dusty rose” (pink), like the photo in this review. You can see some more detailed pics of a red P503i, including screens, on this Japanese page. An English-language PDF detailing the features of this model can be downloaded directly from NTT DoCoMo.