In the area of "strange architecture", I'm surprised that no one
mentioned the Intel iAPX-432. For its time, very unusual.
The GI CP-1600 16-bit CPU had an architecture very similar to the PDP-
11, but used a 10-bit instruction word. I think GI even marketed 10
bit ROMs. These were used in various incarnations as the CPU in many
Activision consoles.
The I2L version of the TI 9900 (SBP 9989?). Not in the architecture
or the instruction set, but the logic family--Silicon Bipolar
Integrated Injection Logic. Like the Fairchild 9440 "micro-Nova sort-
of CPU", virtually unobtainium if you weren't in military aerospace.
Cheers,
Chuck