Few SciSys/Saitek chess computer models can be described in any way as rare but these five qualify, along with the extremely rare SciSys President Chess, and the illusive Turbostar 540+ dealer upgrade of the Turbostar 432 :-

(1) Chess Champion Mark VI + Sensor Board
(2) Courier V
(3) Chess Champion Super System IV
(4) Chess Partner 6000
(5) Renaissance + Sparc module

The first four are in my collection but already covered in the SciSys feature you will find elsewhere on this website.
There you will also find some information about the President Chess and the Turbostar 540+.
The Sparc module is the strongest chess program for the beautiful Renaissance board and that joins the other four in the rare feature. The SciSys Rapier is also scarce but perhaps not sufficiently so to justify an appearance here.