Oh, here’s another one: Lisp Machines. These were computers with alternative chip designs focused on executing Lisp (or really any functional programming language) rather than on executing procedural code. Had the direction been pursued further, they might have resulted in dramatically different computer architectures than what we use today. Some were built and used, but only in very limited contexts, so I’d say this meets the criteria of “never saw the light of day” in that less than 10k Lisp machines were ever built.
Oh, here’s another one: Lisp Machines. These were computers with alternative chip designs focused on executing Lisp (or really any functional programming language) rather than on executing procedural code. Had the direction been pursued further, they might have resulted in dramatically different computer architectures than what we use today. Some were built and used, but only in very limited contexts, so I’d say this meets the criteria of “never saw the light of day” in that less than 10k Lisp machines were ever built.