Newton Messagepad 2000
The Newton 2000 was even a bigger deal.
Complete case redesign.
The Newton 2000 is wider and taller (but thinner) than the 110/120/130 case. It also adds 2 PCMCIA slots and a microphone.
NewtonOS 2.1 provides support for the added features, and the 162mhz StrongARM provides a lot of power.
The only rare 2000 I am aware of is perhaps the EVT2000 developer models that were around before the release of the 2000. While I believe all of those models were supposed to be returned to Apple, I'm sure there are some still floating around out there.