Interesting thread!
I have the following in 1/24:
Tamiya BMW 850i
Hasegawa Nissan R89C (all white metal version)
Hasegawa Williams FW13 (all white metal version)
Fujimi Koenig TR
Tamiya Hi-Ace Delivery Van (don't know if that is rare or not, but never seen it before)
Heller Jaguar E Type
ARII Mercedes 450 SL
Tamiya Opel Calibra DTM Cliff
Tamiya Mercedes C-Class DTM D2
I'm pretty sure people on this forum have more rare ones.